Land Contamination & Reclamation by marc pomel

In this issue: Sustainable remediation: including the external costs of remediation Utilization of drinking-water treatment residue to immobilize copper and zinc in sewage-sludgeamended soils Remediation of soil arsenic toxicity in Ipomoea aquatica, using various sources of organic matter Cover systems for landfills and brownfields Seasonal effect on the load in soil and subsequent transfer of arsenic to rice Elemental profile of abiotic components of the East Calcutta Wetlands, a Ramsar site in India Report of the NICOLE/SAGTA workshop: Sustainable remediation, 3 March 2008, London, UK Clean-up & regeneration bulletin

Land Contamination & Reclamation

EPP Publications

Volume

Number

4 2008

Land Contamination & Reclamation

EPP Publications Ltd

Land Contamination & Reclamation covers all aspects of the contamination and remediation of land, and supplements original research and review papers on the environmental, technical and public health issues with coverage of the commercial and legal context. The journal addresses these topics from national and international perspectives. Contributions are invited for publication in the form of original research papers, case studies, and regional and thematic reviews. Editor

Rupert Hough, PhD, Soil Science Coordinator, The Macaulay Institute, Craigiebuckler, Aberdeen

Europe editor

Tamás Meggyes, PhD, formerly of the Federal Institute for Materials Research and Testing (BAM), Berlin and Visiting Professor, University of Wolverhampton

North America editor

Krishna R. Reddy, PhD, Professor of Civil and Environmental Engineering, University of Illinois at Chicago

Editorial advisory board Professor Brian Alloway Professor Alan J.M. Baker Professor R. Paul Bardos Professor Robert Bell Professor Al Cunningham Chris Evans Bob Harris Professor Hilary I. Inyang Stephen C. James Professor John Mather Fredrick Leong Professor Paul Nathanail Professor Jerome Nriagu Robert W. Puls Michael Quint Michael Smith Professor Paul M. Syms Gordon Wood Peter Wood

University of Reading and University of Plymouth University of Melbourne r3 Environmental Technology Ltd Amec Earth and Environmental Montana State University Arcadis Geraghty and Miller International Ltd National Groundwater & Contaminated Land Centre, Environment Agency The University of North Carolina at Charlotte Sloan93/Xavier University Royal Holloway, University of London Meinhardt China University of Nottingham and Land Quality Management Ltd University of Michigan National Risk Management Research Laboratory, US EPA Arup M.A. Smith Environmental Consultancy English Partnerships Gordon Wood & Company, Chartered Surveyors AEA Technology and University of Reading

Subscriptions The annual subscription (four issues) rates are: companies and other organisations including postage/airmail £107.00 (+ £4.68 VAT if applicable); individuals £59.00 (+ £2.58 VAT if applicable). Available from EPP Publications Ltd, 6 Eastbourne Road, London W4 3EB, UK. Tel. +44(0)20 8400 1601, email: enquiries@epppublications.com, www.epppublications.com Reproduction Apart from fair dealing for the purposes of research or private study, or criticism or review, this publication may not be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photographic or otherwise, without the prior permission in writing of the publisher. Disclaimer The views expressed in the journal Land Contamination & Reclamation are those of the authors alone and do not necessarily reflect those of the editor, editorial board or publisher, or of the authors’ employers or organizations with which they are associated. The information in this publication is intended as general guidance only; it is not comprehensive and does not constitute professional advice. Readers are advised to verify any information obtained from this journal, and to seek professional advice as appropriate. The publisher does not endorse claims made for processes and products, and does not, to the extent permitted by law, make any warranty, express or implied, in relation to the contents of this journal, including but not limited to completeness, accuracy, quality and fitness for a particular purpose, or assume any responsibility for damage or loss caused to persons or property as a result of the use of information in this journal. Cover photo: development at Snow Hill, Birmingham, one of the UK's largest city centre schemes. Courtesy of Bachy Soletanche Limited ISSN 0967-0513. © EPP Publications Limited 2008. Printed in Great Britain by Ashford Press, Southampton EPP Publications Limited • Registered in England and Wales, no. 04596371

Land Contamination & Reclamation Volume 16: Part 4 October 2008

Sustainable remediation: including the external costs of remediation Paul E. Hardisty, Ece Ozdemiroglu and Stuart Arch Utilization of drinking-water treatment residue to immobilize copper and zinc in sewage-sludgeamended soils M. Nur Hanani, I. Che Fauziah, A.W. Samsuri and S. Zauyah

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Remediation of soil arsenic toxicity in Ipomoea aquatica, using various sources of organic matter S.M. Imamul Huq, Shamim Al-Mamun, J.C. Joardar and S.A. Hossain

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Cover systems for landfills and brownfields Georg Heerten and Robert M. Koerner

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Seasonal effect on the load in soil and subsequent transfer of arsenic to rice S.M. Imamul Huq, J.C. Joardar and A.F.M. Manzurul Hoque

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Elemental profile of abiotic components of the East Calcutta Wetlands, a Ramsar site in India S. Chatterjee, B. Chattopadhyay and S.K. Mukhopadhyay

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Report of the NICOLE/SAGTA workshop: Sustainable remediation, 3 March 2008, London, UK Paul Bardos

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Clean-up & regeneration bulletin Policy / regulation Clean-up / regeneration Companies / bodies International Research

405 407 411 412 415

List of key words in Volume 16

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Land Contamination & Reclamation is published by EPP Publications Limited, 6 Eastbourne Road, London W4 3EB, UK. Tel. +44(0)20 8400 1601, email enquiries@epppublications.com, www.epppublications.com

iii

Land Contamination & Reclamation, 16 (4), 2008

DOI 10.2462/09670513.905

Sustainable remediation: including the external costs of remediation Paul E. Hardisty, Ece Ozdemiroglu and Stuart Arch

Abstract Practising sustainable remediation of contaminated sites and groundwater requires a complete understanding of the real costs and benefits of action. A remedial option which is sustainable will result in a net improvement in human welfare, or a net benefit to society. This can be measured explicitly in economic terms by including all of the wider benefits of remediation (to the problem holder and to the rest of society), and all of the costs of remediation, including hidden external costs not normally considered in the remedial decision-making process. If a remedial option is economic in the widest social sense, then it is inherently sustainable, because its result is beneficial to all. Currently, the vast majority of remediation projects undertaken do not consider these wider benefits, and very few explicitly consider the external or hidden costs of remediation – costs which accrue to society as a result of remedial action, intended or unintended. This external damage could include anything from the off-gases produced by aeration-based water-treatment systems (such as airstrippers), the greenhouse gases produced during energy-intensive remediation, and the chlorinated organic compounds generated as daughter products during biodegradation, to the waste tipped in landfills during a typical ‘dig-and-dump’ remediation. In each case, the act of remediating the site has created a secondary effect, which in itself has some effect on the environment, or carries with it some potential for future damage. The costs to society of bearing these secondary effects and liabilities are considered ‘external’ to the problem holder’s own analysis, and consequently have hitherto not been considered in most ‘economic’ analyses. Indeed, the economic impacts of these ‘external costs of remediation’, and their implications for remedial decision-making, have rarely been considered in the literature, and can be considerable. However, a rigorous economic analysis of any remediation option is not complete without considering these oft-neglected external costs. Without considering these costs explicitly, there is every likelihood that the burden of these costs is being shifted unknowingly on to others. Achieving sustainability in remediation requires a like-for-like inclusion of these external costs in an overall economic analysis. Key words: contaminated site management, cost–benefit analysis, decision support tools, environmental economics, remediation, sustainability

INTRODUCTION

Significant amounts of time, effort and money have been devoted to the remediation of contaminated sites

Received August 2008; accepted September 2008 Authors Paul E. Hardisty,1,2 Ece Ozdemiroglu3 and Stuart Arch4 1. WorleyParsons Environmental, Perth, Australia 2. Department of Civil & Environmental Engineering, Imperial College London, UK 3. eftec, London, UK 4. WorleyParsons Environmental, London, UK

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and aquifers. A wide range of methods and technologies have been applied, in conditions as variable as the individual sites themselves. Along the way, consultants, problem holders, individual professionals and government institutions have accumulated a wide knowledge of the costs of remediation and comparison of alternatives based on the costs to problem holders (Teutsch et al. 2001; Bayer et al. 2005; Kaufman et al. 2005). Until very recently, selecting the least-cost remedial option passed for ‘economic’ analysis (Peramaki and Donovan 2003; Goist and Richardson 2003). The benefits to the problem holder were sometimes considered, but the

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

wider benefits to other parts of society were only rarely taken into account (Hardisty and Ozdemiroglu 2005). Borrowing from the wider environmental economics literature (Pearce and Warford 1993), the costs and wider economic benefits of remedial alternatives have been compared to select optimal remediation approaches (Hardisty and Ozdemiroglu 2005). A critical part of this equation, rarely considered, is the social (or external) cost of secondary effects or by-products of a remedial action.

selection of the technological components that will make up the final design.

ECONOMIC MODEL

The external costs of remediation can be framed within an overall economic model describing the full costs and benefits of a particular remedial action. Such an economic model has been presented in Hardisty and Ozdemiroglu (2005). In this analysis, it is assumed that there is full knowledge that the contamination has occurred, and that damage is occurring. Situations in which damage is occurring without the knowledge of the public or regulators, are not considered, though the same method is applicable with added risk/uncertainty. The main variables in the economic analysis are the timing of remedial action, and the spatial context and scope of the action. Therefore, preventive action can be taken now, thus avoiding future damage, or could be postponed, allowing existing damage to continue, and possibly also allowing future damage to occur. The other variable is spatial – the location at which the avoidance or remediation takes place. For instance, a barrier or containment system could be located close to the source, capturing the most concentrated contaminants, and allowing the remainder to escape. Or, if placed further down-gradient, the containment system could capture all of the known contamination. The analysis of Hardisty and Ozdemiroglu (2005) is here expanded to discuss further the external costs of remediation, and as discussed below, the mitigation of these costs.

CONTEXT

At the outset, it is important to distinguish between the different levels at which remedial decisions need to be made. For this discussion, the distinctions between objectives, approaches and technologies are vitally important. These are formally defined below: • Remedial objective is the overall intent of the remediation project. Objectives could include the degree to which groundwater is to be remediated, the protection of specific receptors, or the elimination or reduction of certain unacceptable risks. • Remedial approach is the conceptual manner in which the objective is to be reached, and is defined specifically in terms of the pollutant linkage component it addresses: source removal, pathway elimination, or source protection/isolation. • Remedial technologies are the specific tools which form the components of the approach. For example, physical containment (a pathway elimination approach) can be achieved through use of slurry walls, sheet pile walls, or liners, often in conjunction with groundwater pumping and treatment. Source removal can be achieved through excavation and on-site treatment of contaminated soils (by a variety of techniques), or through many available in situ techniques. A remedial solution will very often involve the use of several different remedial technologies.

In the simplest terms, the economic viability of a given remedial option is assessed by cost–benefit analysis (CBA). If the sum of the benefits of the action over time exceeds the sum of the costs (including the external costs of remediation), given some discount rate, over some planning horizon (time period), then the action is economic, and thus by definition sustainable. The action, which has the highest net present value (NPV), would be chosen as the economic optimum. It is important to note that the often-misused term ‘NPV’ does not simply refer to discounting over time, the ‘net’ in NPV clearly denotes to economists that this is a difference between benefits and costs.

Remedial objectives should be known before detailed design (technology selection) occurs. The choice of a remedial approach is a critical intermediate step, which can be used both as a tool to help set objectives (by considering and comparing various approaches at the conceptual level), and to guide the

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fore, at least in some cases, the later we intervene, the higher the cost of remediation (Cr) will be. To find net benefits, we deduct the flow of costs from the flow of benefits. As an example, the net discounted benefits of prevention and remediation, minus the costs of the selected remediation policy in any year, t, is given by the following equation:

Benefits

Although this paper does not focus on the benefits side of the CBA, the concepts used to describe and value the benefits of remediation may also be used when quantifying external costs. In determining an optimal remedial objective, the benefits of the action must be considered. Equally, secondary impacts (sometimes called dis-benefits, but referred to here as external costs) of the action may also occur, and these also have to be taken into consideration in a complete analysis.

NPV : ARt =

Economic theory dictates that the over-arching policy is to maximize human welfare, in the context of the present value. Thus, we would select the action and time-phasing that maximizes the NPV of benefits and costs. Let ‘baseline’ damages be D(t) (damages that occur when no action is taken). Typically, dD/dt > 0, since the contamination may migrate over time, potentially impacting a greater number of receptors. Other scenarios where dD/dt < 0 may also occur (natural degradation of contaminants over time). D(t) can in fact be a complex function, depending on the nature of the contaminant, speed of movement, assets at risk and the economic value of those assets. If we remediate, then the benefits are equivalent to the damage avoided from the moment that the objective is achieved, onwards (or prevention of future damages which would have occurred if the remedial action had not been taken), and can be expressed as the new (lower or perhaps eliminated) damage function D(t):A, or simply Dt:A. We may include action to clean up (remediate) damage already incurred, yielding a new damage function Dt:ARt, where A stands for avoidance, or prevention of further damage, and R denotes remediation of existing damage.

 Dt − Dt : ARt − C : ARt   (1+ r ) t  

∑

where NPV is the net present value of the net benefits over time; NPV:ARt is NPV conditional upon the A and R mix of intervention which takes place; C is the aggregate cost of prevention (of further damage) and remediation (of existing damage) (Cp + Cr), and r is the discount rate. If the prevention or remedial actions taken produce a secondary impact, then it should be included in the analysis as an external cost of remediation. External costs of remediation are conceptually similar to negative benefits, in that they are damages which accrue over time, as impacts on stakeholders or resources. Thus, as long as they continue, they will accumulate. External costs of remediation can be expressed as X:ARt, depending on the nature of the effect produced by the remedial activity. It is assumed that these costs reflect the residual damages which occur as secondary impacts of the main remediation, after the application of available mitigation measures. The cost of implementing these mitigation measures (Cxm) is also considered, resulting in a revised NPV expression: NPV: ARt =

 Dt − Dt : ARt − C : ARt − C xm : ARt − X : ARt   (1+ r ) t 

∑ 0

Net benefits and external costs

What is important in a decision-making process is not only the magnitude of benefits, but also the magnitude of the costs that will bring about the said benefits, and hence the term ‘cost–benefit’ analysis. For simplicity, assume that the prevention costs (Cp), are the same regardless of when we intervene, i.e. Cp,t = Cp,t+1 and so on. This implies that it costs the same (in current year prices) to adopt a preventive policy, regardless of when we act. In practice, Cp may vary. Remediation costs, on the other hand, will tend to vary with size of plume, type of contaminants, and the nature of the geological and aquiferous material and properties. There-

REMEDIAL COSTS

For each remedial objective being considered, a number of possible remedial approaches may be possible, each employing different technologies. For each approach, the technology or suite of technologies which can most efficiently achieve the stated objective, at the lowest possible cost, is what is required for a CBA. Remediation engineers perform this type of analysis on a daily basis, based on experience and a growing worldwide database of case histories and research.

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There is often a wide choice of available technologies that can be employed in a remedial approach design. Each technique may involve many subcomponent options. Each of the decisions on option choice will be based in part on cost, and each choice will have cost implications. The basic elements of developing a preliminary remedial cost estimate are shown in Table 1. External costs of applying the method are not included in this table.

EXTERNAL COSTS OF REMEDIATION

As discussed in the introduction, the act of remediation can cause secondary effects which may result in an environmental impact in their own right, despite our best attempts at mitigation. These effects must be included in the overall economic assessment, if optimal remedial decisions are to be made. If the costs of dealing with these effects, or the damages which they cause, are not borne by the problem holder, then they are termed external costs of remediation (Hardisty and Ozdemiroglu 2005). External costs of remediation (Cx) can be divided into two categories: (1) planned or process-related external costs which cannot or will not be mitigated against (Cxp); and (2) unplanned, inadvertent or unforeseen external costs (Cxup), such that:

Note that the discount rate selected for the cost analysis will have a significant effect on PV costs. Often, for a complete social (economic) analysis, a ‘social discount rate’ is used that reflects the time preference and cost of capital to the society as a whole. In the UK, HM Treasury provides guidance for the social discount rate (HM Treasury 2003). Some other countries and international organizations also have similar guidance. Often, in private financial project analysis, much higher discount rates are used, reflecting desired corporate internal rates of return and costs of capital. This reflects one of the key differences in perspective between the problem holder and other stakeholders – the private sector is generally seeking higher and more immediate returns, while society as a whole (including the problem holder) is typically less concerned with return on capital invested.

Cx = Cxp + (P × Cxup) where P is the probability that the unplanned cost will occur. Each of these is discussed below. Planned external costs

Many of the remedial solutions which are used today involve some degree of unmitigated secondary damage or liability to the environment or to another party. Depending on the regulations being enforced in a

Table 1. Cost analysis for remedial approach analysis Cost category

Annual cost estimate

Capital cost estimate

Uncertainty (+/–) range

PV estimate

Uncertainty

ONE-TIME COSTS Design and engineering Mobilization Preparatory/enabling works Capital costs – initial Capital costs – future modification ON-GOING COSTS over selected planning horizon Operation Maintenance Treatment Monitoring Validation POST-TREATMENT COSTS Decommissioning Total cost

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particular jurisdiction, these can vary from minor residual effects, to major planned transfers of cost. A good example is the common practice of landfilling of wastes excavated from contaminated sites. Removal of concentrated zones of soil contamination by excavation is a common way of removing the source of on-going groundwater contamination. Contaminated soil seen to be posing an unacceptable risk at a site is excavated and transported to a secure landfill facility. Of course, the definition of secure varies depending on which part of the world is being considered. Even in developed and well-regulated jurisdictions, landfills have been known to leak and themselves become sources for sub-surface contamination. Excavation and land filling (or ‘dig-and-dump’ as it is often known) can cause external costs in several ways: 1.

Potential damage to the receiving environment at the landfill. Unless the landfill site is 100% secure, there is the potential that the wastes may generate leachate or vapour releases which may contribute to impacts on the surrounding environment, particularly groundwater. While the overall impact of the remediation may have been positive, in that there has been an overall net reduction in the potential for the waste to harm human health or the environment, now that it is sequestered in the landfill, it remains as a potential source of long-term risk. The wastes have simply been transferred from one location to another, and now must be managed and contained over the long term. Valuation of this cost is difficult in practice. A highly conservative approach would be to include in external costs the cost of destroying or otherwise rendering the wastes inert through some form of ex situ treatment. The fees paid by the problem holder to the operator of the landfill represent the costs of mitigation against release of any portion of the waste into the environment, where it could cause damage. The external cost represents the residual impact, based on the probability of release of part of that waste, despite containment efforts.

health from emissions; noise impacts; and increased probability of accidents. An average cost of $0.78/vehicle-km can be estimated, based on recent studies by Newberry (1992) and Maddison et al. (1996), and statistics provided by the UK Department of Transport (2002). The example below describes how this estimate of the external costs of transport would affect the economic analysis of a remediation using ‘dig-and-dump’. The external costs associated with the emissions of greenhouse gases (GHG) during the entire remediation. To the degree that GHG emissions are taxed in a given jurisdiction, these would theoretically be included within the internal costs, in a purely financial analysis. In a wider social analysis, these levies would constitute transfer payments, and would not be included. Estimates of the external costs of GHG emissions are provided by Stern (2006), and, more recently, DEFRA has published updated guidance on the use of the shadow price of carbon (DEFRA 2007, 2008), expressed in dollars and pounds sterling per tonne of CO2 equivalent (CO2e).

Example: external costs of transport to landfill The expected journey for road transport of excavated waste from a remediation project will make use of mainly trunk roads and highways. The distance from the site to the secure landfill is 400 km (which is not uncommon in the UK as landfills become more scarce), and, assuming that the vehicles complete a return journey, the total journey length is 800 km. It is expected that 10 000 tonnes of contaminated soil need to be excavated and removed to landfill. At an average of 20 tonnes per HGV, 500 vehicle movements will be required to complete the trip. Relevant economic valuation studies suitable for benefits transfer to estimate the external costs of transport are provided below. Tables 2 and 3 provide information on studies investigating costs due to congestion, noise, health and accidents. An external cost for each impact is calculated, as shown below, and then the three external costs are aggregated to provide a total unit cost for heavy vehicle movements.

The external costs of transporting waste to landfill using heavy-goods vehicles (HGVs). These can be estimated, based on the assumption that increased HGV traffic on the road network will result in a number of costs: increased congestion; impacts on

Road congestion The remedial programme will result in one thousand additional long road journeys that otherwise would not

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Table 2 Valuation of road congestion Reference

Impact type

Change being valued / valuation scenario

Method

Results

Newberry (1992)

Congestion

HGV traffic marginal cost of congestion on different types of road – United Kingdom

Mix

(UK £/HGV km) Motorway £0.006 ($0.0108) Urban central peak £0.8347 Urban central off-peak £0.6708 Non-central peak £0.3639 Non-central off-peak £0.2006 Small town peak £0.1581 Small town off-peak £ 0.0964 Other urban £0.0019 Rural main £0.0016 ($0.0029) Other trunk £0.0044 ($0.008) Other rural £0.0012 ($0.0022)

have been undertaken. This adds to the congestion of roads along the planned route, and has a measurable economic impact. Table 2 shows relevant information on valuation of road congestion. Considering the mix of road types used in the journey shown in Table 2 (movements: motorway (28%); trunk (57%); rural dual carriageway (13%); and other rural (2%)), a unit cost for congestion per vehicle per km can be calculated:

Unit cost of health and noise per HGV km: = $0.6309 + $0.0412 = $0.672 per vehicle-km ($2002)

Table 3. External costs of road transport – health and noise ($2002/km)

Unit cost of congestion per HGV km:

Costs

HGV

Bus/coach

Passenger car

Health*

0.6309

0.4206

0.0421

Noise

0.0412

0.2754

0.0139

* Pollutants considered: PM10, SOx, NOx, VOCs, lead, benzene Source: Maddison et al. (1992), UK £ = 1.8 US $

= ($0.0108 × 0.28) + ($0.008 × 0.57) + ($0.0029 × 0.13) + ($0.0022 × 0.02) = $0.003 + $0.0045 + $0.0004 + $0.000044 = $0.0080 per vehicle-km ($2001) = $0.009 per vehicle-km ($2002)

Accidents and fatalities The additional truck movements will bring a statistical probability (albeit very small) that an accident involving one of the vehicles will occur during the course of the remediation. Statistics are available which allow the cost of this possibility to be estimated, as shown in Table 4. Using the figures in Table 4 in conjunction with an estimate for the value of a statistical life presented in Table 5, an estimate for the unit cost of a fatality and serious injury per vehicle-km is calculated.

Health and noise The planned truck movements will generate additional noise along the route, and will generate additional health impacts, primarily as a result of air emissions from exhaust and dust. These impacts will be felt by people living along the planned route. These people have no involvement in the remediation programme, and will not benefit directly from the remediation. Thus, costs of remediation are being shifted on to them, and must be accounted for in a complete economic analysis. Table 3 details results of recent valuation studies of these impacts. Applying the values in Table 3 to the example, unit external costs of transport related to noise and health impacts resulting from the vehicle movements for transport of excavated soil to landfill would be estimated as:

Unit costs of accidents per vehicle-km: = $0.084 + $0.0177 = $0.102 per vehicle-km ($2002) Total external costs of transport Using all of the information above, the total external costs for transporting the material to the landfill using

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contaminant type, tipping fees, and the complexity of the dig. In this example, the expected private or internal cost for remediation using ‘dig-and-dump’ was expected to be approximately $3.2m. Adding $0.3m to reflect the real cost of the remedy, represents a 10% increase. Note also that if clean fill has to be imported to the site to fill in the excavation, additional vehicle movements will be required, further boosting the external cost of transport. Furthermore, the other possible external costs of landfilling have not yet been added. Examples of other types of planned external costs of groundwater remediation are listed in Table 6. In general, planned external costs are increasingly being mitigated against. In many jurisdictions, specific regulatory measures are being put in place to ensure that remediation methods which deliberately shift costs from the problem holder to society are reduced or eliminated. Recent examples in the European Union are the Landfill Directive, which puts stringent new limits on landfilling of hazardous wastes excavated from remediation sites, and the Environmental Liability Directive, which has the potential to hold the polluter responsible for rectifying external damages.

Table 4. Accidents associated with heavy vehicle traffic in the UK ($2002/km) Total fatalities due to HGVs in 2001 (A)

588

Total serious injuries due to HGVs in 2001 (B)

2910

Total vehicle kilometres by HGVs in 2001 (billions) (C)

29.2

The average risk of fatality per vehicle km for HGVs (D)

0.20 × 10–7

The average risk of serious injury per vehicle km for HGVs (E)

1.00 × 10–7

The cost of serious injury measured as the willingness to pay (WTP) to avoid injury (F)

$177,220

Source: Transport Statistics Great Britain, taken from the Department for Transport website (UK Department for Transport 2002)

Table 5. Value of a statistical life ($2002) The cost of fatality measured as the value of a statistical life (G)

$4,206,438

Total cost of fatality per vehicle km for HGVs (D × G)

$0.084

Total cost of serious injury per vehicle km for HGVs (E × F)

$0.0177

Unplanned external costs

Accounting for unplanned or unforeseen costs of remediation is of course problematic; we may not know that they are going to happen, or we may have discounted them as only a remote possibility. Sometimes, despite best planning and care, remediation activities result in the creation of a secondary impact on the environment, or on other stakeholders. If the impact is an unplanned or unforeseen result of remediation, for which mitigation measures have not been provided or have not been successful in countering, then the value of this damage is included as an external cost of remediation. Table 7 provides examples of unplanned external costs. Accounting for unplanned external costs within an economic evaluation of remedial alternatives is not straightforward. For any given remedial approach being considered, the possibility that its implementation may cause additional external damages must be carefully evaluated. In most situations, experienced remediation engineers and specialists should be able to identify possible secondary damage. In all cases, mitigation measures should be put into place to deal with these possibilities. Whatever probability remains of

heavy road-vehicles can be calculated as the sum of congestion, health, noise and accident-related external costs: Total unit external costs of transport per vehicle-km = costs of congestion + health + noise + accidents = $0.01 + $0.67 + $0.10 = $0.78 per vehicle-km ($2002) Using the unit cost of $0.78/vehicle-km, the total external cost of transporting the excavated contaminated soil from the site to the landfill can be estimated. For 500 vehicle movements, each involving a 800km round-trip, a total cost of $312,000 is calculated. In this case, this represents the costs borne by others as a result of the additional vehicle traffic which resulted from the decision to use the dig-and-dump method to remediate this site. The relevance of this impact can be seen by considering typical private remediation costs for excavation and landfilling of 10 000 tonnes of contaminated soil. A typical remediation programme of this size would cost in the order of $2m to $5m, depending on location,

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Table 6. Examples of planned external costs of remediation Activity

Secondary effect

Comments

Air-stripping of volatile compounds from groundwater, without off-gas treatment

Release of volatile compounds to atmosphere

Still occurs in many jurisdictions; can be mitigated against

Thermal treatment of contaminated soils

Release of CO2 and other gases to atmosphere

Greenhouse-gas emissions

Permanent sequestering of contaminated groundwater

Permanent loss of injected groundwater as a resource

Widely used for difficult and recalcitrant contaminants

Excavation of concentrated source of contamination to protect underlying groundwater, results in habitat destruction

Habitat in excavated area is destroyed

Mitigation â&#x20AC;&#x2DC;bankingâ&#x20AC;&#x2122; approaches can be used to offset

Table 7. Examples of unplanned external costs of remediation Activity

Secondary effect

Example

Remediation causes LNAPL to revert to DNAPL, due to preferential removal of lighter compounds

NAPL sinks, contaminating a new volume of aquifer, worsening the dissolved-phase problem

SVE (soil vapour extraction) preferentially removes volatile aromatics from an LNAPL containing less-volatile dense compounds

Bioremediation results in creation of daughter products which are more toxic than the parent

Toxicity to receptors increases

TCE (trichloroethene) degrades to VC (vinyl chloride), and VC persists in the aquifer

Remediation inadvertently increases the mobility of contaminants within the aquifer, through alteration of physiochemical properties

Impact on receptors worsens, either due to further spreading of the plume, increased mass flux, or more rapid breakthrough

Surfactant flush greatly increases dissolution of NAPL

Remediation inadvertently increases the mobility of contaminants within the aquifer, through alteration of the properties of the aquifer itself

Impact on receptors worsens, either due to further spreading of the plume, increased mass flux, or more rapid breakthrough

In situ fracturing of aquifer to enhance NAPL recovery inadvertently allows increased NAPL mobility towards receptors

Remediation compromises adjacent confining layers or geological features

Contaminant is introduced into a hitherto uncontaminated geological unit

Pumping wells completed across a confining layer, cross-connecting two groundwater-bearing zones

number of sub-surface storage tanks into a shallow unconsolidated gravel aquifer. DNAPL has over time accumulated atop a thin low-permeability clay unit which overlies and hydraulically isolates an underlying fractured aquifer that is used for local water supply. A nearby public water-supply well pumps from the bedrock aquifer. The thickness of the clay unit directly beneath the DNAPL accumulation varies from about 0.5 m to 2 m.

that damage occurring, after the mitigation measures are put in place (and the cost of their implementation added to the overall cost of remediation Cr), it should be applied to the value of the damage anticipated should the event occur. Assigning a probability to an eventuality that is being mitigated against is a matter of professional judgement for the remediation team, and should be based on experience, knowledge of the limitations of remedial technologies and the nature of the mitigation measures themselves.

One of the remediation approaches being considered includes excavating and removing the bulk of the DNAPL from the gravel to prevent further dissolvedphase migration within the gravel, to reduce risk to public water supplies using the bedrock aquifer, and to make the site suitable for redevelopment. This remedial

Example: remediation of DNAPL in a partially saturated gravel unit A site is contaminated by DNAPLs (dense nonaqueous-phase liquids) which have migrated from a

314

Sustainable remediation: including the external costs of remediation

estimated for road transport associated with remediation.

approach would include excavation and removal of underground tanks and DNAPL-contaminated gravels, followed by on-site soil-washing to reduce as much as possible the need for off-site landfilling. The most efficient way to excavate the gravel would be to pile into the clay unit, preventing the inflow of groundwater into the excavation, and allowing removal of the contaminated gravels rapidly and cost-effectively (wet excavation is typically more difficult and more expensive). After washing, clean gravels would be replaced in the excavation, and contaminated fines landfilled. Table 8 shows estimated costs for this option.

In addition, an estimate of the total greenhouse-gas (GHG) emissions generated during the remediation, including from the energy-intensive soil washing and excavation activities, also represents an external cost. Social costs of GHG emissions were estimated using the approach recommended by the UK government (DEFRA 2007, 2008), which currently values the shadow price of carbon at $52/t CO2e. Using the estimated total emissions for the remediation project of 1200 t CO2e (including HGV emissions), an external PV cost of US $62,500 is estimated. It is noted that this is a lower estimate than Sternâ&#x20AC;&#x2122;s (2006) central estimate of the social cost of carbon (US $85/t CO2e). The selection of the approach to the cost of carbon may vary between jurisdictions. However, the uncertainty in cost reflected by these two approaches may be used in sensitivity analyses to examine the influence that changes in carbon cost may have on outcomes.

For a complete economic analysis of this option, however, the external costs must be considered. In this example, it is assumed that the problem-holder has undertaken a complete audit of the landfillâ&#x20AC;&#x2122;s procedures and waste containment and management systems, and have satisfied themselves that wastes tipped there have a very low probability of being released to the environment, so as to assume that external costs are zero (or, more strictly, too low to make a significant difference to the total costs). In the UK, where there is a landfill tax to capture the external costs of landfilling (HMRC 2008), the tax payment is added to the tipping fees to capture the full cost. In this example, this cost would be $640 000 ($64/tonne). In addition, the landfill is over 200 km from the site, and the vehicle movements required to execute the remediation amounted to about 800,000 km, based on an average heavy-goods vehicle capacity of 10 m3. Based on the unit estimates discussed above, external costs of US $312,000 are

There is also a risk that piling into the clay unit may open up pathways for DNAPL migration into the bedrock aquifer below. If this were to occur, then a significant dissolved-phase plume would develop in the fractured aquifer, which modelling results show would impact the nearest public water-supply well within 100 days, at concentrations that would knock the well out of production. What is more, removal of the DNAPL from the fractured bedrock would be extremely difficult, if not impossible. The possible unintended external costs of this option, as part of a remedial approach decisionmaking process, could be based on the estimated

Table 8. Cost estimate â&#x20AC;&#x201C; remediation of contaminated gravels Item

Basis

Cost (US$)

Mobilization and set-up

Site facilities, security, traffic management

175,000

Piling

(7 m deep, x 400 linear m) interlocking piles

550,000

Excavation

Excavate gravels, replace clean material, material handling and stockpiling as necessary

1,650,000

Water treatment

Dewatering systems, water-treatment system to meet local sewer discharge criteria

450,000

Gravel washing

Wash 30 000 m3 of gravels

1,100,000

Land-filling fines

Landfill 5000

Professional fees

Design and supervision, validation, reporting

500,000

Total estimated cost

Private (internal) cost only

5,325,000

of fines

900,000

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Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

annual value of the public water supply (PWS) water production eliminated as a result of contamination. Given the licensed abstraction rate of 100 000 m3/yr, the commercial value of the well is estimated at US $240,000/yr, or a PV of US $3.4m over 20 years at a social discount rate of 3.5%. Assuming that there is a 25% probability (as a worst-case estimate) that the basal layer could be pierced during piling, an additional notional external cost of US $850,000 is estimated (essentially a risk premium). Of course, in reality, if the basal layer were to be pierced, and the aquifer were to be damaged, then the site owner would potentially be liable for the entire value of the lost water supply, and these notional external costs would almost certainly become an internal cost.

proposition is thus unsustainable (Hardisty and Ozdemiroglu 2005). Notwithstanding this conclusion, it is noted that cost–benefit analysis is only one input to the decision-making, so decisions may still be taken in the knowledge of, but contrary to, the recommendations of such an analysis. This may be not only because it is not always possible to quantify all costs and benefits, but also because there may be other factors (e.g. corporate social responsibility, legal requirements, etc.) that dictate a given solution regardless of the CBA findings.

SUMMARY AND CONCLUSIONS

Economic analysis, encompassing both private (the problem holder) and external (the rest of society) costs and benefits, provides a tool for answering one of the fundamental questions of contaminated-site remediation – should we remediate, and if so, to what level? Simply put, if the sum of all the benefits of remediation, including those which accrue to the problem holder and more widely to society as a whole, exceed the total costs of repairing the damage – given some discount rate and planning horizon, and including the secondary costs of damage to the environment caused during the remediation process – and there are potentially many, depending on the methods used), then economic theory states that the project would be worth doing, and would therefore be sustainable, since society’s overall welfare would be improved.

Taking all into account, for this remediation design alternative, the estimated cost of the remedial action itself is US $5.325m, to which external damage costs of US $1.865m are added for a total cost of US $7.2m. Thus, when comparing this remedial option to other alternatives, the overall social cost of the remedial effort is about 35% greater than would normally have been estimated. In this case, the risks and costs associated with possible impacts to the lower aquifer were judged to be too great, and a modified remedial alternative was selected, involving stopping the piling just above the basal clay layer, and managing the increased water flow into the excavation. This alternative resulted in substantially higher water-treatment, pumping and energy costs, adding approximately US $650,000 to the overall internal costs, but removing the US $850,000 external cost from the comparative estimate.

Once a decision has been made to remediate, a specific remedial objective is required. Remedial objectives may take many forms, from a basic containment strategy (ensure no further migration of contaminants within the aquifer), to a programme of extensive cleanup, perhaps to some risk-based standard. The full costs and benefits of these different objectives will typically vary considerably. Inclusion of the often hidden external costs of remediation is critical in assessing the true economics of an option, and thus its sustainability. As shown above, external costs take many forms: from emissions to atmosphere; to the public dis-amenity of increased vehicle traffic during remediation; to the generation of solid wastes. These external costs can be significant, and may have an effect on the final choice of remedial approach. When combined with economic considerations of the benefits of remediation, this anal-

However, as discussed above, achieving remediation that is truly sustainable requires much more than the choice of the lowest-cost (internal and external costs included) approach. In this example, after we have included the external costs, the question becomes: is the US $7.2m total cost actually justified? Will the expenditure of the problem holder and the damage incurred by society to undertake this remediation result in an overall increase in human welfare? Simply put, if the value of the benefits of remediation to all stakeholders exceeds US $7.2m, then it is worth proceeding, and the remediation is sustainable. If the value of benefits is significantly less than US $7.2m, then the remediation is probably not worth doing, and the

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Sustainable remediation: including the external costs of remediation

ysis can be used to rank remedial objectives, and assist in choosing an objective that makes economic sense for all stakeholders. Thus defined, economic options are sustainable, and uneconomic ones are not, since all of society’s costs and benefits are included.

Hardisty, P.E. and Ozdemiroglu, E. (2005) The Economics of Groundwater Protection and Remediation. CRC Press, NY HMRC (2008) Rationale for the UK Landfill Tax. Her Majesty’s Revenue and Customs, http://www.hmrc.gov.uk/manuals/lftmanual/LFT1040.htm

Clearly, economic analysis of remedial objective options is only part of a complete decision-making process. Any decision must take place in a wider context of the constraints of remediation (time, budgets, physical limitations, legal and legislative regulations, and the requirements of government policy). Each of the stakeholders involved in a particular site or issue will have their own view on each of these considerations, and a complete and fair decision-making process must include and value all of these.

HM Treasury (2003) The Green Book. London Kaufman, M.M., Rogers, D.T. and Murray, K.S. (2005) An empirical model for estimating remediation costs at contaminated sites. Journal of Water, Soil & Air Pollution, 167 (1– 4), 365–386 Maddison, D., Pearce, D.W., Johansson, O., Calthorp, E., Litman, T. and Verhoef, E. (1996). The True Costs of Road Transport. Earthscan, London Newberry, D. (1992) Economic principles on pricing roads. Oxford Rev. Econ. Policy, 6, no. 2

REFERENCES

Pearce, D.W. and Warford, J.J. (1993) World Without End. World Bank

Bayer, P., Finkel, M. and Teutsch, G. (2005) Cost-optimal containment plume management with a combination of pump-and-treat and physical barrier systems. Groundwater Monitoring & Remediation, 25 (2), 96–106

Peramaki, M.P. and Donovan, P.B. (2003) A remedial-goal driven, media-specific method for conducting a cost benefit analysis of multiple remedial approaches. Proc. NGWA Conf. on Remediation: Site Closure and the Total Cost of Cleanup. New Orleans, Nov. 2003

DEFRA (2007) The Social Cost of Carbon and the Shadow Price. What They Are and How to Use Them in Economic Appraisal in the UK. DEFRA, London

Stern, N. (2006) The Economics of Climate Change. The Stern Review. Oxford University Press

DEFRA (2008) The Shadow Price of Carbon: Response of Government Economists to Academic Peer Review Comments. DEFRA, London

Teutsch, G., Rugner, H., Zamfirescu, D., Finkel, M. and Bittens, M. (2001) Source remediation vs. plume management: critical factors affecting cost-efficiency. Land Contamination & Reclamation, 9 (1), 128–139

Goist, T.O. and Richardson, T.C. (2003) Optimizing cost reductions while achieving long term remediation effectiveness at active and closed wood preserving facilities. Proc. NGWA Conf. on Remediation: Site Closure and the Total Cost of Cleanup. New Orleans, Nov. 2003

UK Department for Transport (2002) Transport Statistics Great Britain, Department of Transport website (www.dft.gov.uk)

Apart from fair dealing for the purposes of research or private study, or criticism or review, this publication may not be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photographic or otherwise, without the prior permission in writing of the publisher. The views expressed in this and in all articles in the journal Land Contamination & Reclamation are those of the authors alone and do not necessarily reflect those of the editor, editorial board or publisher, or of the authors’ employers or organizations with which they are associated. The information in this article is intended as general guidance only; it is not comprehensive and does not constitute professional advice. Readers are advised to verify any information obtained from this article, and to seek professional advice as appropriate. The publisher does not endorse claims made for processes and products, and does not, to the extent permitted by law, make any warranty, express or implied, in relation to this article, including but not limited to completeness, accuracy, quality and fitness for a particular purpose, or assume any responsibility for damage or loss caused to persons or property as a result of the use of information in this article.

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Land Contamination & Reclamation, 16 (4), 2008

ÂŠ 2008 EPP Publications Ltd

DOI 10.2462/09670513.903

Utilization of drinking-water treatment residue to immobilize copper and zinc in sewage-sludge-amended soils M. Nur Hanani, I. Che Fauziah, A.W. Samsuri and S. Zauyah

Abstract In situ immobilization of copper and zinc using alum-treated drinking-water treatment residue (WTR) was selected for the remediation of sewage-sludge-amended soils. The WTR has a pH of 7.07 and, although its acid-neutralizing capacity (ANC) is low, utilization at high rates (>2.5%) can help to increase the pH of the soil system. The minerals present in WTR, such as kaolinite, gibbsite and Feoxides, provide surfaces for the adsorption of heavy metals. From the soil-solution study, results showed that application of WTR had reduced Zn concentrations in the soil solutions, as compared to the control treatment. Removal of Zn occurred via precipitation, adsorption and possibly organicmatter complexation or chelation. From the glasshouse study, results showed that by using WTR, Zn uptake by maize can be reduced. Although the decrease in Cu concentrations in the soil-solution study was not apparent, due to the very low concentrations of Cu present, the glasshouse study did indicate a reduction in Cu uptake by the maize plants; suitable rates of WTR application for maize growth should be less than or equal to 10%. In fact, there is an additional benefit of WTR application, whereby the rate of 2.5% can increase the dry weight of the maize plants. Thus, WTR can be recommended as a potential soil amendment to immobilize Zn in contaminated soil. Key words: acid soil, alum-treated water treatment residue, maize growth performance, soil-solution study

INTRODUCTION

In situ immobilization is a cost-effective approach whereby land-applied amendments are used to stabilize contaminants via adsorption and/or precipitation reactions that render the contaminant immobile (Adriano 1986). Numerous inorganic materials, such as clays, Al/Fe/Mn oxides and hydroxides may be used as soil amendments for metal-contaminated soils, as a means of reducing metal mobility. A low-cost and potentially effective substitute for natural Al hydroxides could be drinking-water treatment residues (WTRs). In this study, alum-treated WTR was used to fix or stabilize

Received February 2008; accepted May 2008 Authors M.I. Nur Hanani, I. Che Fauziah,* A.W. Samsuri and S. Zauyah, Department of Land Management, Faculty of Agriculture, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia. Email fauziah@agri.upm.edu.my * Author to whom correspondence should be addressed

319

heavy metals in soil treated with sewage sludge. Longterm application of sewage sludge will cause accumulation of heavy metals such as Cd, Cu, Ni, Pb and Zn in both the soil and plants (Sloan et al. 1997). However, one problem that must also be addressed with regard to WTR application is the P-fixing capability of WTR in the soil system. Phosphorus deficiency associated with land application of WTR has aroused extensive research interest recently. Heil and Barbarick (1989) and Lucas et al. (1994) reported P deficiency in plants grown at the highest WTR application. Therefore, the suitability of these materials for land application must first be evaluated. Thus, in order to use WTR successfully for agricultural purposes, careful analytical monitoring of its composition and subsequent controlled rate of application to the soil would be required. There is evidence in the literature that total soil metal content alone is not a good measure of short-term bioavailability, and neither is it a useful tool to determine the potential risks from soil contamination (Tack

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

The sewage sludge and soil samples were also subjected to the same determinations, except for the ANC determination.

and Verloo 1995; Sauvé et al. 2000). On the other hand, soil porewater is critical to environmental bioavailability, mobility and geochemical cycling of metals in soil. The compositional analysis of metals in porewater is frequently more informative than those of the whole soils or soil extracts (Wolt 1994). To validate these findings, the growth performance of an indicator or test crop has been evaluated.

Physical characterization

The WTR was subjected to surface-area determination using the Brumnauer, Emmet and Teller (BET) technique, and the particle-size distribution was determined using Day’s pipette method (Day 1965).

The overall objectives of this study were to assess the suitable rates of WTR application for agricultural purposes, and its potential or capability to reduce the plant-available heavy metals, and also to determine the limitations of WTR usage.

Mineralogical characterization

Mineralogical characterization was carried out on the WTR samples by X-ray diffraction (XRD), using a Philips (PW 3050/60) X’Pert PRO diffractometer and a Cu Kα radiation source.

MATERIALS AND METHODS

Water-treatment residue (WTR) was taken from Puncak Niaga Sdn. Bhd. in Sabak Bernam, Selangor, Peninsular Malaysia. This was an alum-treated WTR. The sewage sludge used in this study was collected from the Indah Water wastewater treatment plant in Gombak, Selangor. The soil used for all the experiments in this study was the topsoil (0–20 cm) of a Bungor Series soil (clayey, kaolinitic, isohyperthermic family of a Typic Paleudult) (Tessens and Shamshuddin 1979), which was taken from the UPM Puchong Experimental Farm. The WTR, sewage sludge and soil samples were air-dried, ground, and sieved through a 2.0-mm sieve before the laboratory analyses were conducted.

PHOSPHORUS SORPTION STUDY

Different concentrations of P solution (0, 100, 200, 300, 400 and 500 mg L–1) were added to 10 g of sample. The adsorbed P was determined by the difference between the input concentration and the concentration left in the soil solution at equilibrium. The amount of P left at equilibrium was determined using the Murphy and Riley (1962) colorimetric method. The samples were: S1 S2 S3

WTR only Soil only Soil + 5% WTR

CHARACTERIZATION OF WTR

SOIL-SOLUTION STUDY

Chemical characterization

A laboratory incubation study was carried out, whereby WTR was applied to the Bungor Series soil. Twentyfour pots were arranged in a completely randomized design (CRD), which consisted of six treatments and four replicates. A rate of 5% of sewage sludge, which was established during preliminary studies, was added to each pot. The treatments were as follows:

A sample of WTR was analysed for moisture content; pH (1:2.5 soil:H2O ratio); exchangeable bases (K+, Ca2+ and Mg2+) and cation-exchange capacity (CEC) using 1 N NH4OAc, adjusted to pH 7.0 (Thomas 1982); the basic cations were determined using the PerkinElmer PE 5100 atomic absorption spectrophotometer; total carbon by a total carbon instrument LECOCR412; total nitrogen by the Kjeldahl method; total Al and heavy metals by aqua regia (1:3 HNO3:HCl) digestion, after which the metals were also determined using an atomic absorption spectrophotometer; and acidneutralizing capacity (ANC) by the batch titration method using an incremental volume of 0.5 M HCl.

T1 T2 T3 T4 T5 T6

320

Soil + 5% sewage sludge + 0% WTR Soil + 5% sewage sludge + 2.5% WTR Soil + 5% sewage sludge + 5% WTR Soil + 5% sewage sludge + 10% WTR Soil + 5% sewage sludge + 20% WTR Soil + 5% sewage sludge + 40% WTR

Utilization of drinking-water treatment residue to immobilize copper and zinc in sewage-sludge-amended soils

Soil solutions from the incubation study were extracted using a Rhizon soil moisture sampler (Eijelkamp, the Netherlands). This consisted of a length of porous, chemically inert hydrophilic plastic (2.5 mm o.d., 1.4 mm i.d, average pore diameter c. 0.1 µm), capped with nylon at one end, and attached to a 10 cm length of syringe. The deionized water was added to the soil at 21% of moisture content (16% field capacity). The porous tip of the Rhizon soil moisture sampler was mounted in the soils. The pressure created and the vacuum in the syringe would draw the solution from soil. After 48 hours, about 10 mL of the soil solutions were collected from each of the syringes. The soil was incubated in the laboratory for 70 days and from days 0 to 70 the soil solutions were collected once a week. The soil solutions were analysed for pH and water-soluble Cu and Zn for all treatments, using the Perkin-Elmer PE 51000 atomic absorption spectrophotometer (AAS).

Plant sample preparation and analyses

Maize was harvested at maturity – about 70 days after sowing. After harvest, fresh and dry plant weights were determined. Then the maize tissue was dried in an oven (65–70°C) until a constant weight was recorded. The dried tissue was ground to pass a sieve size of 0.1 mm. Macronutrients, with the exception of nitrogen (Kjeldahl digestion method) and Cu and Zn in the tissue, were determined using the dry ashing method. Between 1 and 2 g of air-dried tissue sample were ashed in a muffle furnace at 300°C for one hour, and at 500°C for a further four hours. The cool ash was digested with 2 mL of 20% nitric acid, and was then heated on a hot plate for 15 minutes. Then the sample was ashed again in a muffle furnace at 300°C for one hour, and at 500°C for a further four hours. The ashed sample was left to cool to room temperature. Later, it was digested again with 2 mL of deionized water and 2 mL of HCl, and then heated again on a hot plate for 15 minutes. A volume of 10 mL of 20% nitric acid was added and the digest was heated further in a water bath at 100°C for one hour. It was then filtered into a 100 mL volumetric flask and made up to volume with distilled water. The Cu, Zn and macronutrient (K, Ca and Mg) concentrations were determined using the PE 5100 AAS.

GLASSHOUSE STUDY

The study was conducted in the glasshouse unit of the Faculty of Agriculture, Putra University, Malaysia. Twenty pots were arranged in a completely randomized design (CRD). There were four treatments, and each treatment was replicated four times. The treatments were: T1 T2 T3 T4 T5

The validity of the plant-digestion procedures and the ICPS operating parameters was established using the internationally recognized National Institute of Standard and Technology (NIST) maize grain standard material, NIST 8433.

Soil + 5% sewage sludge + 0% WTR (control) Soil + 5% sewage sludge + 2.5% WTR Soil + 5% sewage sludge + 5% WTR Soil + 5% sewage sludge + 10% WTR Soil + 5% sewage sludge + 20% WTR

The data obtained were subjected to analysis of variance (ANOVA) using the Statistical Analysis System (SAS 1988) and, where significant, the means were compared by using Duncan multiple range tests.

Maize (Zea mays L.) was used as the test crop. Three plants per pot were grown in 3 kg of a Bungor Series Soil; and sewage sludge at a rate of 5%, which was established during previous studies, was added as a source of nitrogen. To each of the pots, P was applied as triple superphosphate (TSP) and K as muriate of potash (MOP) at the rate of 100 kg of P ha–1 and 140 kg of K ha–1 for all treatments, respectively.

RESULTS

The chemical characteristics of the WTR, sewage sludge and Bungor Series soil are shown in Table 1. The sewage sludge used in this study was an acidic sludge. The C:N ratio of the sludge is about 9.5:1, which is close to the mineral soil C:N ratio. The percentage of total N and available P for this sewage sludge fall within the typical ranges of 3–5% N and 0.1–4.5% P, respectively. The sludge contains substantial amounts of ammonium acetate extractable plant

Soil chemical analyses

The dried WTR-amended soil samples were analysed for pH (1:2.5 soil:H2O ratio), and electrical conductivity (EC) (1:5 soil:H2O). 321

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

Table 1. Chemical properties of WTR, soil and sewage sludge used in this study Al-WTRa

Bungor soila

Sewage sludgea

ECSb

7.07

4.72

4.42

n.a

CEC (cmol (+) kg–1)

8.27

6.07

n.d

n.a

ANC (% CCE)

0.504

n.d

n.a

Total C (%)

2.27

0.97

31.02

n.a

Total N (%)

0.23

0.06

3.33

n.a

Total P (%)

0.012

3.12

0.48

n.a

Exch. K (%)

0.010

0.31

3.75

n.a

Exch. Ca (%)

0.23

0.52

0.21

n.a

Exch. Mg (%)

0.002

0.17

0.87

n.a

Total Al (%)

11.2

n.d

n.a

Total Zn (mg kg–1)

103.07

1.80

2300.08

1000–1750

Total Cu (mg kg–1)

4.93

0.40

107.29

n.a

Total Cd (mg kg–1)

0.43

n.d

2.86

2500–4000

Total Pb (mg kg–1)

58.80

n.d

73.29

n.a

Total Ni (mg kg–1)

13.73

n.d

23.61

20–40

ANC acid-neutralizing capacity expressed in % calcium carbonate equivalence (CCE). CEC cation-exchange capacity. n.a not available. n.d. not determined. a results are average of three replicates. b ECS (maximum permitted concentration of sewage sludge according to the Commission of the European Communities Directive (1986)

Ippolito et al. (2000) and Elliott et al. (1990). The ANC of WTR was 0.504% CCE. Thus, WTR cannot be considered to be a good liming material as compared to pure CaCO3, but use of this material at high rates can still increase the pH of acidic soil. The CEC value for the WTR was found to be 8.27 cmol (+) kg–1, which is be considered to be low. The carbon for this WTR is close to the typical value of 3%, and was within the range of 0.85 to 6.5% (Elliott et al. 1990). The percentage of total N was similar to results reported by Rengasamy et al. (1980), which were between 0.5 and 1% total N. Clearly, the WTR cannot be considered as a source of supplementary N fertilizer. The concentration of total P falls within the range that is mostly found in soil (100–3000 mg kg–1). Values for exchangeable Ca, Mg and K concentrations were very low in the WTR. The values were found to be lower as compared to the ranges of these elements found in soil (Adriano et al. 1980).

macronutrients such as K and Mg. The concentrations of heavy metals (Cu, Ni, Cd and Pb), with the exception of Zn, were well below the concentrations found in ECS guideline (maximum permitted concentration of sewage sludge according to the Commission of the European Communities Directive). This is supported by McGrath et al. (1995), who found that the levels of heavy metals in domestic sewage sludge and sewage sludge treated with advanced technology are very low and negligible, respectively, with the exception of Zn and sometimes Cu. The Bungor Series soil is one of the common soil series in the country. The soil is acidic in nature, and normally this soil would be limed before any crop is grown on it. From Table 1, the fertility status of the soil can be considered to be low. The CEC of this soil was 6.07 cmol (+) kg–1, and thus the cation retention capacity of the soil is low.

The Al content of the WTR is considered to be very high, because aluminium sulphate was added as a coagulant during the drinking-water treatment process in the water-treatment plant. Because alum-based WTR contains Al, this might be of concern if WTR is land

CHARACTERISTICS OF THE WTR Chemical characteristics

The pH for WTR for this study was close to neutral, just as stated in the reports by Gallimore et al. (1999),

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Utilization of drinking-water treatment residue to immobilize copper and zinc in sewage-sludge-amended soils

applied, as there might be an increase in Al in the soil solution, which has the potential to be phytotoxic. Concentrations for Zn, Cu, Ni, Cd and Pb were well below the concentrations found in most soils, and the ECS guidelines (maximum permitted concentration of sewage sludge stipulated by the Commission of the European Communities Directive). Previous studies have shown that most WTR have low concentrations of regulated metals (Bugbee and Frink 1985; Elliot and Singer 1988; Lucas et al. 1994; Peters and Basta 1996).

PHOSPHORUS SORPTION STUDY

The P adsorption study was conducted for WTR (S1), soil (S2), and soil treated with WTR (S3) samples. The maximum adsorption capacity of the S1 could not be determined from the data. S1 exhibited H-type isotherms, which indicate that P was very highly adsorbed and had not reached the maximum adsorption. P adsorption for S2 and S3 can be described using the Langmuir equation (Table 2). The linear form of the Langmuir equation is:

Physical characteristics

C/q = 1/ (Kb + Cb)

The moisture content in WTR is only 11.7%. WTR have a silty clay texture, which is in accordance with the report by El-Swaify and Emerson (1975), which stated that, physically, WTR behaves like clay. The value of surface area for WTR was largely dependent on the size of the sample, which was less than 2 mm, due to the grinding or pulverization process.

where: C is the equilibrium concentration (mg L–1) q is the amount of chemical adsorbed (mg kg–1) K is the adsorption constant that is related to binding strength (L mg–1) b is the maximum amount of the chemical that can be adsorbed by the soil (mg kg–1).

Mineralogical properties

An X-ray diffraction analysis (XRD) of the clay minerals of the WTR is given in Figure 1. The minerals present in WTR were kaolinite (0.721 and 0.357 nm) and some amounts of other minerals, such as gibbsite (0.486 nm) and quartz (0.426 and 0.333 nm), as reflected by their corresponding peaks.

Kim et al. (2003) reported that the maximum adsorption capacity of WTR was 25 g kg–1 for orthophosphate. It was obvious that WTR adsorbed much more P than the soil. The maximum adsorption capacitities for S2 (soil only) and S3 (soil + 5% WTR) were estimated to be 1.5 g of P kg–1 and 1.75 g of P kg–1,

Counts/s

600 Q 500 400 300 200

Q K

100 0

2 THETA ANGLE

K is kaolinite, Q is quartz and G is gibbsite

Figure 1. X-ray diffractogram of a powder sample of water-treatment residue

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6.00 5.80 5.60 5.40 pH

5.20 5.00 4.80 4.60 4.40 4.20 4.00 1

Time (week) 0%

2.5%

10%

20%

40%

Figure 2. The pH values at different rates of WTR treatments in the soil-solution study during ten weeks of WTR incubation

respectively. The soil and soil + 5% WTR have almost the same maximum adsorption value for P.

Heavy metals

Zinc and Cu concentrations in soil solutions for all treatments during the ten weeks of incubation are shown in Figures 3 and 4, respectively. Zinc showed a positive response, that is, reduction in the watersoluble concentrations due to increasing rates of WTR treatments. On the other hand, for Cu, there seemed to be no significant reduction in the solution concentrations due to WTR application.

Table 2. Values of R2 (regression coefficient), b and K from linearized, transformed P-adsorption isotherms, using the Langmuir equation R2

b (mg kg–1) max. adsorption

K (L mg–1) binding affinity

0.927

1500

0.152

0.979

1750

0.417

Sample

For zinc, at week seven, treatment using the highest rates of WTR (40%) gave the lowest Zn concentration. Perhaps the high Zn concentrations and high pHs at the higher WTR rates led to low solubility of Zn, due to the pH effect and also the phenomenon known as ageing (Lock and Janssen 2003). The trend of Zn solubility indicates slow dissolution of Zn minerals at the initial stage, and then the concentration dropped again due to precipitation or to the ageing affect. Zinc concentrations were found to be low in all treatments using different rates of WTR (2.5, 5, 10, 20, and 40%), as compared to the control (0% WTR). The addition of WTR reduced the release of Zn from the sewage sludge. Therefore, WTR can be considered to be a potential soil amendment to fix Zn in contaminated soils. Copper concentrations in soil solutions were found to be very low in all treatments, including the control, which were less than 1 mg L–1. However, the

S2 – soil only; S3 – soil + 5% WTR

SOIL-SOLUTION STUDY pH effect

The soil pH, is regarded by soil chemists as a master determinant or a master variable controlling process in the soil–plant system, because it not only influences processes directly through the toxic effect of the H+ ion, but also indirectly through its controlling influence over the solubility and availability of plant nutrients to plants and animals (Wolt 1994). The pH values of WTR incubation treatments are presented in Figure 2. The pH value for all treated soils increased by almost one unit during the ten weeks of incubation, irrespective of rates.

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Utilization of drinking-water treatment residue to immobilize copper and zinc in sewage-sludge-amended soils

6.00

-1

Zinc (mg L )

5.00 4.00 3.00 2.00 1.00 0.00 1

TIME (week) 0%

2.5%

10%

20%

40%

Figure 3. Soluble Zn at different rates of WTR treatments in the soil-solution study during ten weeks of WTR incubation

0.10 0.09 -1

Copper (mg L )

0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00 1

Time (week) 0%

2.50%

10%

20%

40%

Figure 4. Soluble Cu at different rates of WTR treatments in the soil-solution study during ten weeks of WTR incubation

40.00 35.00

a ab

Weight (g)

30.00

25.00

20.00 15.00 10.00 5.00 0.00

2.5%

WTR

10%

20%

Similar letters above bars indicate that the values represented by the bars are not significantly different at the 1% level, according to the Duncan new multiple range test (DMRT)

Figure 5. Dry weight of maize at different rates of WTR treatments

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Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

Table 3. Comparisons of macronutrients and macronutrient sufficiency ranges (NSRs) for maize Macronutrients

5% Sewage sludge + rates of WTR (%)

NSR (%)a

2.5

N (%)

1.20

1.27

1.08

1.13

0.97

3.50–5.00

P (%)

0.15

0.16

0.15

0.13

0.10

0.30–0.50

K (%)

1.66

1.29

2.09

2.14

2.15

2.50–4.00

Ca (%)

0.82

0.65

0.71

0.75

0.82

0.30–0.70

Mg (%)

0.33

0.25

0.27

0.31

0.35

0.15–0.45

Data showed adequate ranges of macronutrients for maize growth (Mills and Jones 1996)

Table 4. Comparisons of micronutrients and micronutrient sufficiency ranges (NSRs) for maize Macronutrients Zn (mg kg–1) Cu (mg kg a

–1)

5% Sewage sludge + rates of WTR (%)

NSR (mg kg–1)a

2.5

152.75

91.50

105.25

81.00

75.65

20–60

8.00

7.50

2.75

3.33

2.67

5–20

Data showed adequate ranges of micronutrients for maize growth (Mills and Jones 1996)

treatments after four weeks of sowing, because visible

addition of WTR did not seem to significantly reduce the Cu concentrations in the soil solutions.

K deficiency was detected; that is, the older leaves exhibited necrosis at the edges of the leaf blades. Even though visible symptoms of N deficiency were not

GLASSHOUSE STUDY

detected, this NSR comparison showed that the addiMaize dry weight

tion of 5% sewage sludge does not supply adequate N

The dry weights of maize for WTR treatments are shown in Figure 5. The dry weights of maize progressively decreased with the addition of 5, 10 and 20% WTR. This is in agreement with previous research, which found that plants grown in the soil amended with WTR decreased in dry weight with an increasing ratio of WTR treatments (Rengasamy et al. 1980; Elliot and Singer 1988; Lucas et al. 1994).

for maize growth. For the micronutrient sufficiency range data for maize, only concentrations for Zn and Cu are available (Table 4) (Mills and Jones 1996). Concentrations of Zn in plant tissues were found to be higher than the sufficiency range required for maize growth. The concentrations of Zn were considered to be very high, and can affect the quality of the plant. The control had the high-

Nutrient sufficiency range (NSR) for macronutrients and micronutrients

est Zn concentration, which indicates the presence of high amounts of Zn in sewage sludge. With the addi-

Concentrations of N, P, K, Ca, and Mg were compared with the nutrient sufficiency range (NSR) of maize, in order to assess whether WTR has an effect on the adequate range of macronutrients for plant growth (Table 3). Concentrations of Ca and Mg were found to be sufficient for maize growth in all the treatments. Phosphorus deficiency occurs in maize grown on WTR-treated soil, due to its ability to fix P in the soil system (Elliot et al. 1990). Concentrations of N and K were found to be low compared to the NSR for maize growth for WTR. Therefore, additional K (140 kg ha–1) was added to all

tion of WTR (2.5, 5, 10 and 20%), the uptake of Zn was reduced. Copper concentrations in plant tissues grown in soil amended with WTR, and for the control were found to be within levels adequate for maize growth. The uptake of Cu was highest for the control, which indicates the presence of high amounts of Cu in the sludge. Significant reductions in Cu concentrations in plant tissues were also observed with the increase in the rates of WTR addition.

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Utilization of drinking-water treatment residue to immobilize copper and zinc in sewage-sludge-amended soils

amended soil can significantly reduce the uptake of Cu by maize.

Macronutrients and selected heavy metals uptake by maize

Figure 6a shows the nitrogen (N) uptake by maize that was grown in soil treated with WTR. In this study, the source of N was solely from the addition of sewage sludge. The addition of 5% of sewage sludge was not able to provide sufficient N for maize growth. The highest N uptake was from the 2.5% WTR treatment, which was significantly different from the control and the rest of the treatments. The phosphorus (P) uptake by maize treated with WTR is shown in Figure 6b. With regard to WTR treatment, P concentrations were found to be highest and significant for treatments using 2.5% WTR, as compared to other treatments, including the control. From this study, it cannot be concluded with certainty whether or not P sorption or precipitation was reduced due to the formation of an organo-P complex in the presence of sewage sludge. This needs to be investigated further. As shown in Figure 6c, there was a significant difference in potassium (K) uptake by maize treated with 5% WTR as compared to the control (0% WTR) and the rest of the treatments, with the exception of the 10% application of WTR. Concentrations of K in plant tissues were found to be low compared to the level adequate for maize growth. Therefore, additional K needs to be supplied to the WTR treatments. The uptake of calcium (Ca) by maize using WTR is shown in Figure 6d. The Ca concentrations in plant tissues were within or higher than the sufficiency range required for maize growth. Figure 6e shows the magnesium (Mg) uptake by maize treated with WTR. Magnesium concentrations were found to be significant for 0, 2.5 and 5% WTR, as compared to the 10 and 20% WTR rates. The concentrations of Mg in plant tissues were within the sufficiency range required for maize growth. Figure 7a shows the uptake of Zn by maize. Addition of WTR significantly reduced Zn uptake as compared to the control. These results show that using WTR mixed with sewage sludge can significantly reduce the uptake of Zn by maize. The major effect of high pH was to reduce the solubility of all micronutrients, especially Zn. Figure 7b shows the uptake of Cu by maize. The addition of more than 5% WTR significantly reduced Cu uptake as compared to the control. These results show that using more than 5% WTR in sewage-sludge-

DISCUSSION

Incorporation of WTR into the soil can change soil moisture and structure. Bugbee and Frink (1985) observed that soil moisture retention and aeration improved with the addition of WTR, while Rengasamy et al. (1980) observed increased soil aggregates, accompanied by an increase in soil water holding capacity when WTR was added. This aspect of the benefits of WTR amendment was not investigated in this study. The concern over the presence of a high Al content in WTR can be allayed by the findings of Elliot et al. (1990) and Peters and Basta (1996), that land application of alum-based WTR did not increase dissolved Al in surface run-off or extractable Al in soil. Aluminium in WTR exists as insoluble Al-oxide in soil environments that are only slightly acidic (pH > 5). Using WTR as a soil amendment will reduce dissolved and extractable P in soil (Cox et al. 1997; De Wolfe 1990; Peters and Basta 1996). There are chemical constituents in WTR capable of adsorbing and precipitating dissolved P (e.g. Al-oxides and Fe-oxides). Kaolinite, which is present in WTR, has also been recognized for its reactivity with phosphate ions (Basta et al. 2005). The solid Al(OH)3 has also been reported to be able to remove P by adsorption. According to Heil and Barbarick (1989), the P adsorption capacity of WTR is a function of WTR age, pH, particle size and surface area. Surface-area determination can be used to estimate the number of surface sites available for surface complexation reactions. Butkus (1998) reported that the surface area of WTR was 10 m2 gâ&#x20AC;&#x201C;1. Dzombak and Morel (1990) reported that WTR can bind with protons, cations and anions, with sorption maxima ranging from 160 to 600 m2 gâ&#x20AC;&#x201C;1. Clay minerals can contribute to chemical reactions in soil because of their comparatively large surface area with permanent negative charges. The mineralogy of highly weathered tropical soil is dominated by kaolinitic and sesquioxide clay, and this leads to the presence of kaolinite in WTR. When alum (Al2 (SO4)3.14H2O) is added to water, it dissociates to give trivalent Al3+ ions, which hydrate to form Al (H2O)63+. 327

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

b) 6b

600 a

500 400

U p t a k e o f P ( m g p o t -1 )

U p t a k e o f N ( m g p o t -1 )

a) 6a

b bc cd

300

200 100 0 5%

10%

8 6

20%

a b

d) 6d

U p t a k e o f C a ( m g p o t -1 )

U p t a k e o f K ( m g p o t -1 )

2.5%

70 60

c) 6c

50 40 30 20 10 0

2.5%

25 20

10%

20%

10%

20%

15 10 5 0

2.5%

10%

U p take o f M g (m g p o t -1 )

e) 6e

20%

2.5%

a ab

10 8

6 4 2 0 0%

2.5%

10%

20%

Similar letters above bars indicate that the values represented by the bars are not significantly different at the 1% level, according to the Duncan new multiple range test (DMRT)

Figures 6 aâ&#x20AC;&#x201C;e. Uptake of macronutrients by maize plants (mg potâ&#x20AC;&#x201C;1), using soil amended with WTR

328

Utilization of drinking-water treatment residue to immobilize copper and zinc in sewage-sludge-amended soils

Uptake of Zn (mg pot -1)

a) 7a

5.000

4.000

3.000

2.000

Uptake of Cu (mg pot -1)

1.000 0.000 0%

b) 7b

10%

20%

0.300 0.250

2.5%

0.200 0.150 0.100

0.050 0.000 0%

2.5%

10%

20%

Similar letters above bars indicate that the values represented by the bars are not significantly different at the 1% level, according to the Duncan new multiple range test (DMRT)

Figures 7aâ&#x20AC;&#x201C;b. Uptake of heavy metals, Zn (a) and Cu (b) by maize plants (mg potâ&#x20AC;&#x201C;1), using soil amended with WT

soil system, therefore, the influence of organic matter on P-retention was not known with certainty.

The Al ion undergoes a series of rapid hydrolytic reactions to form soluble monomeric and polymeric species as well as Al (OH)3 or gibbsite. The X-ray diffraction

The immobilization of heavy metals using WTR is thought to involve a combination of three processes: increase in pH; specific or chemisorption; and complex-formation or chelation with organic matter. An increase in soil pH results in a corresponding increase in the net negative charge of variably charged colloids in soils, such as clays, organic matter and Al hydroxides. This can result in an increase in heavymetal sorption and hence a reduction in the soluble metal concentrations in soils. Also, the high content of Al hydroxides in WTR introduces new sorptive surfaces which may immobilize heavy metals in soils, through specific or chemisorption. Finally, interaction of heavy metals with organic matter should also be

analysis of WTR indicated the presence of gibbsite. Also, the low CEC value of WTR suggests that adsorption might not be the main mechanism by which heavymetal content in soils is lowered. In the P sorption study, the pH of the soil mixture was not controlled. The pH of the WTR-only sample is almost neutral, whereas the pH of the soil-only sample is acidic at around 4.72. Also, in this adsorption study, only 5% WTR was added to the soil, whereas the highest treatment rate for the soil-solution study was 40% for WTR, and for the glasshouse study it was 20% WTR. Besides, no sewage sludge was present in the

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Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

2.5 dS m–1, a 10% yield reduction has been reported for maize (Bohn et al. 1985). For availability of plant nutrients, liming to a pH between 5.0 and 5.5 has been recommended for Bungor Series soil (Shamshuddin et al. 1991). The pH of the WTR-treated soil for this study ranged from 5.00 to 5.80 which should be suitable for maize growth.

given due consideration, due to the presence of the sludge in the soil system. The high affinity of some heavy metals – especially copper, and to some extent zinc – for organic matter is well known, and it has two consequences. In the presence of dissolved organic matter, metal mobility increases as metal–humic acid and metal–fulvic acid complexes are formed (Hsu and Lo 2000). On the other hand, upon soil acidification, non-soluble high-molecular-weight organic acids can retain significant concentrations of metals in soils (Chirenje and Ma 1999).

Heavy-metal concentration is not a very sensitive parameter to indicate crop responses to WTR application as compared to crop uptake data. This is due to the fact that the metal concentrations can sometimes be masked by the differences in the biomass production for the different WTR treatment rates.

According to Harter and Naidu (1995), a pH value greater than six was effective in lowering free metal ion activities in soils. Liming can enhance the retention of metals in soils, thereby reducing their availability for uptake by plants (Adriano 2001). Increasing the soil pH has been shown to be more effective than other soil parameters in reducing heavy-metal availability in contaminated soils (Gray et al. 1998). Although the acidneutralizing capacity (ANC) of WTR was only 0.504% CCE, high rates of WTR application were able to increase the pH of all the treated soils by at least one pH unit. In the present study, it was not possible to ascertain how much of the decrease in metal availability after the application of WTR was due to increase in soil pH, and how much was due to specific adsorption or soil ageing.

CONCLUSION

In WTR, the concentrations of the major macronutrients used for plant growth are relatively low, and so this by-product cannot be a good fertilizer supplement if it is used alone. Also, based on the P-sorption study, the solubility of phosphorus in WTR-amended soil is considered to be one of the limitations associated with the use of WTR as a soil amendment. Therefore, it is important to supply additional P fertilizer if WTR is to be used in agricultural soil. In the glasshouse study, the suitable rates of WTR for maize growth are 2.5, 5.0 and 10%. In the soil-solution study, WTR application has the ability to reduce the solubility of Zn in the soil system. The uptake of Zn by maize was significantly reduced at 2.5% WTR application, as compared to the control treatment. The textural class of WTR is silty clay, which is suitable for mixing into sandy soil to improve soil structure. Also, although the ANC of WTR is low, utilization at high rates (>2.5%) can help to increase the soil pH. The minerals present in WTR, such as kaolinite, gibbsite and Fe-oxides, can reduce Zn mobility and availability in soil, by adsorption, (co)precipitation or a combination thereof. Moreover, the organic matter present in the sludge can also have an influence on zinc mobility. Copper immobilization by WTR in the soil system cannot be shown with certainty in this study, that is, contradictory results were obtained from the glasshouse and the soil-solution studies.

Both the C:N ratios of WTR and sewage sludge are close to the C:N ratios of the mineral soil. The total C in WTR is stable and resistant to degradation, properties which are similar to those of soil organic C (Elliott et al. 1990). The same can be said regarding the organic matter in the sewage sludge that was used in this study. Therefore, the latter mechanism of organic-matter interaction – that is, significant concentrations of metals can be retained in the soil upon soil acidification – is likely to have taken place in the soil–WTR–sludge system. Plants grown in the soil amended with WTR decreased in dry weight with increasing WTR treatment ratios (Rengasamy et al. 1980; Elliot and Singer 1988; Lucas et al. 1994). A possible explanation for this result is that it is likely to be due to the influence of the concentration of soluble salts in the soil system. The EC means for the soil treated with different rates of WTR ranged from 1.6 to 2.0 dS m–1, with the control having a mean EC value of 1.4 dS m–1. At an EC of

This study indicates that land application of WTR can be recommended because of its effectiveness in fixing or stabilizing heavy metals, especially Zn, in

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Utilization of drinking-water treatment residue to immobilize copper and zinc in sewage-sludge-amended soils

contaminated soil, through changes in soil pH and also through adsorption on the mineral surfaces, such as the Al-hydroxide surfaces in alum-treated WTR. The use of WTR at up to 10% showed no significant detrimental effect as compared to the control treatment. The glasshouse study also indicates an additional benefit, whereby 2.5% of WTR can increase maize weight. Hopefully, the results of this study can give some insight into the utilization of WTR as a soil amendment for agricultural purposes.

Chirenje, T. and Ma, LQ. (1999) Effects of acidification on metal mobility in a papermill-ash amended soil. J. Environ. Qual., 28, 760–767

ACKNOWLEDGEMENTS

Day, P.R. (1965) Particle fraction and particle size analysis. In: Methods of Soil Analysis (Part 2) (ed. C.A. Black et al.) pp. 1367–1378. American Society of Agronomy, Wisconsin

Commission of the European Communities (EU) (1986) Council Directive (86/278/EEC) on the protection of the environment, and in particular of the soil, when sewage sludge is used in agriculture. pp. 6–12. Off. J. European Community L181 (Annex 1A) Cox, A.E., Camberato, J.J. and Smith, B.R. (1997) Phosphate availability and organic transformation in an alum sludge affected soil. J. Environ. Qual., 26, 1393–1398

We would like to thank the drinking-water treatment plant, Puncak Niaga Sdn. Bhd., for supplying us with the WTR used in this study. Also, we would like to thank UPM for giving us permission to carry out this project under the Fundamental Research Grant Scheme FRGS 03-07-03-0705, and to publish this research work. Special thanks go to Ms. Rosazlin Abdullah for the preparation of this manuscript.

De Wolfe, J.R. (1990) The Effects of Land Applied Alum and Ferric Chloride Water Treatment Sludges on Soil Phosphorus. M.Sc. thesis, Dept. of Civil Engineering, Pennsylvania State University Dzombak, D.A. and Morel, F.M.M. (1990) Surface Complexation Modelling: Hydrous Ferric Oxide. Wiley, New York Elliott, H.A. and Singer, L.M. (1988) Effect of water treatment sludge on growth and elemental composition of tomato shoots. Comm. in Soil Sci. & Plant Anal., 19, 345–354

REFERENCES Adriano, D.C. (1986) Trace Elements in Terrestrial Environments (ed. D.C. Adriano). Springer, New York

Elliott, H.A., Dempsey, B.A., Hamilton, D.W. and De Wolfe, J.R. (1990) Land Application of Water Treatment Sludges: Impacts and Management. American Water Works Assoc. and AWWA Research Foundation, Denver, CO

Adriano, D.C. (2001) Trace Elements in Terrestrial Environments: Biogeochemistry, Bioavailability and Risks of Metals (ed. D.C. Adriano), 886 pp. Springer, New York

El-Swaify, S.A. and Emerson, W.W. (1975) Changes in the physical properties of soil clays due to precipitated aluminium and iron hydroxides: I. Swelling and aggregate stability after drying. J. Soil Sci. Soc. Am., 39, 1056–1063

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Gallimore, L.E., Basta, N.T., Storm, D.E., Payton, M.E., Huhnke, R.H. and Smolen, M.D. (1999) Water treatment residual to reduce nutrients in surface runoff from agricultural land. J. Environ. Qual., 28, 1474–1478

Basta, N.T., Zupancic, R.J. and Dayton, E.A. (2005) Evaluating soil tests to predict Bermudagrass growth in drinkingwater treatment residuals with phosphorus fertilizer. J. Environ. Qual., 29, 2007–2012 Bohn, H.L., McNeal, B.L. and O’Connor, G.A. (1985) Soil Chemistry (ed. H.L. Bohn). Wiley, New York

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Hsu, J.H. and Lo, S.L. (2000) Characterisation and extractability of copper, manganese and zinc in swine manure composts. J. Environ. Qual., 29, 447–453

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Land Contamination & Reclamation, 16 (4), 2008

ÂŠ 2008 EPP Publications Ltd

DOI 10.2462/09670513.900

Remediation of soil arsenic toxicity in Ipomoea aquatica, using various sources of organic matter S.M. Imamul Huq, Shamim Al-Mamun, J.C. Joardar and S.A. Hossain

Abstract Various sources of organic matter (namely poultry litter, cow dung and sewage sludge) were used to remediate arsenic accumulation in plants (Ipomoea aquatica) in a pot-culture experiment. Organic matter was applied at the rates of 5 t/ha and 10 t/ha to soils spiked with arsenite at 20, 50 and 100 mg As/kg soil. Plants were grown for 30 days after germination. The presence of arsenic in the growth medium had a negative impact on the vegetative growth of the plants, for both organic matter treatments and control. However, organic-matter application had a more positive effect than no application, at all levels of arsenic spiking. Poultry litter performed the best, and at the application rate of 5 t/ha, the vegetative growth was more than 81.55% over the control; whereas the increases were 17.74% and 10.98%, respectively, for cow dung and sewage sludge at the same rate of application. Organic-matter application was able to reduce arsenic accumulation by as much as 75% in the vegetative part of the plant. For the various sources of organic matter, the performance in reducing the accumulation of As in Ipomoea aquatica followed the order: poultry litter > cow dung > sewage sludge. Key words: arsenic, Ipomoea aquatica, organic matter, remediation

nation exceeding the WHO guideline level of 10 g/L (BGS/DPHE 2001). Bangladesh is currently facing the challenge of mitigating soil contamination related to arsenic-laden groundwater irrigation. About 40% of the total arable land of Bangladesh is now under irrigation, and more than 60% of irrigation needs are met from groundwater extracted by deep tube-wells, shallow tube-wells or hand tube-wells (Imamul Huq and Naidu 2005). Approximately 27% of STWs and 1% of DTWs in 270 upazilas (sub-districts) of the country are classified as contaminated with As according to the Bangladeshi standards, whereas about 46% of STWs are classified as contaminated according to the WHO standard. So far 38 000 people have been diagnosed, with an additional of 30 million people at risk of As exposure (APSU 2005). The widespread use of Ascontaminated groundwater for irrigation has been reported to pose the risk of As build-up in soil, and its subsequent transfer to plants and vegetables (Imamul Huq et al. 2001; Ali et al. 2003; Imamul Huq and Naidu 2003; Imamul Huq and Naidu 2005; Imamul Huq et al. 2006b). The average soil As level is below 10 mg/kg, with values exceeding levels as high as 80 mg/kg in

INTRODUCTION

Arsenic (As) contamination in the groundwater was reported in Bangladesh during the early 1990s. Extensive contamination in Bangladesh was confirmed in 1995, when a further survey showed contamination of mostly shallow tube-wells (STW) across much of southern and central Bangladesh (Imamul Huq et al. 2006a). More than 35 million people in Bangladesh are exposed to As contamination in drinking water exceeding the national standard of 50 g/L, while an estimated 57 million people are at risk of exposure to As contami-

Received July 2008; accepted August 2008 Authors S.M. Imamul Huq,* Shamim Al-Mamun, J.C. Joardar and S.A. Hossain, Bangladeshâ&#x20AC;&#x201C;Australia Centre for Environmental Research (BACER-DU), Department of Soil, Water and Environment, University of Dhaka, Dhaka-1000, Bangladesh Corresponding author: Dr. S.M. Imamul Huq, Professor and Chairman, Department of Soil, Water and Environment, University of Dhaka, Dhaka1000, Bangladesh. Tel. 88-02-9661920-73/7478, 4590 (office); 88-01819 227377 (mob.), fax 88-02-8615583, email imamh@bttb.net.bd; imamhuq@hotmail.com

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areas where irrigation using As-contaminated water is practised continuously, and the annual build-up from irrigation in soil has been calculated to be 5.5 kg/ha (Imamul Huq and Naidu 2005). The form of arsenic found in the groundwater is mostly As(III). In more than 90% of cases, As in groundwater occurs in this form (Imamul Huq and Naidu 2003). It has been observed that the arsenic in irrigation water and the water-soluble fraction of soil arsenic is more bioavailable than the total fraction (Imamul Huq et al. 2003). The release and retention of As in the soils of Bangladesh have been found to be governed by, among other factors, the clay fraction and the clay mineralogy of the soils (Joardar et al. 2005; Imamul Huq et al. 2006a; Imamul Huq et al. 2006c). Numerous greenhouse/field studies have found that an increase in As in cultivated soils leads to an increase in the levels of As in edible vegetables (Helgensen and Larsen 1998; Burló et al. 1999; Carbonell-Barrachina et al. 1999; Chakravarty et al. 2003; Farid et al. 2003), with many factors affecting bioavailability, uptake and phytotoxicity of As (Carbonell-Barrachina et al. 1999). Furthermore, phytotoxicity due to increased arsenic in soil/water, and its longterm impact on agricultural yield, are also major concerns (Ali et al. 2003). Combating the adverse effects of arsenic will be of prime importance in the years to come. Novel strategies have to be developed in this area. One strategy could be to amend the soil in such a way that the materials used for amendment would not degrade the soil properties, but rather improve them. Such a strategy could involve the use of organic matter that might be able to reduce the phytoavailability of arsenic.

1988; Shiralipour et al. 2002; Molla and Imamul Huq 2004; Kwiatkowska and Maciejewska 2006; Martins et al. 2006). Inorganic arsenic is methylated to lesstoxic, and perhaps less-labile, organic arsenic, which could be a strategy to remediate As-contaminated soils for crop production, thus minimizing As transfer to plants. We have tried other remedial possibilities, such as water-regime manipulation (Imamul Huq et al. 2006d), and using green and blue-green algae (Imamul Huq et al. 2007). These tests were performed on rice. However, production of vegetables in Ascontaminated areas also carries the risk of As accumulation in the produce (Farid et al. 2003; Imamul Huq et al. 2006b; Sanyal et al. 2007). The present work is a further extension of our attempts to remediate As-contaminated soil using cheap and easily available organic sources. The present work aims to study the impact of cow dung, poultry litter and sewage sludge on controlling the transfer of As from soil to plants, and to compare the effectiveness of the different sources of organic matter in this regard.

MATERIALS AND METHODS

The experiment was conducted in the net house of the Department of Soil, Water and Environment, University of Dhaka, Bangladesh, during April to September 2006. Sampling site

Soil from a farmer’s field in Dhamrai, Savar, near Dhaka, was selected for sampling. The soil belonged to the Dhamrai soil series (UN Development Programme and Food and Agriculture Organization of the UN 1998; Imamul Huq et al. 2006d, 2007). The location of the sampling area is 23°54.776' N and 90°10.938' E (Figure 1). According to the USDA Soil Taxonomy the soil is a Typic Endoaquept and is mixed and non-acid; according to the General Soil Type it is a Non-Calcareous Grey Floodplain Soil (GST No. 6), and according to the FAO-UNESCO Legend it is a Chromi-Eutric Gley Sol.

In Bangladesh, there are many dairy farms that have been producing large volumes of cow dung. About eight million metric tonnes of cow dung were used as fuel in 1997, and a large amount of cow dung was used annually as domestic fuel in rural areas (BBS 2004). Poultry litter is another important source of organic matter that can be used on agricultural land. Today, poultry manures are becoming popular in some areas of Bangladesh. Sewage sludge has been found to be effective when used in combination with fertilizer as an additional source of nutrients in agriculture, in order to economize on fertilizer costs (Sikder et al. 2007).

Soil sample collection and sample preparation

The bulk soil samples representing depths of 0– 150 mm depth below the surface were collected using the composite soil sampling method, as suggested by the soil survey staff of the United States Department of

Composts and cow dung have been found to reduce the phytoavailability of As, Cd, Pb and Zn (Erickson

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Remediation of soil arsenic toxicity in Ipomoea aquatica, using various sources of organic matter

Kilometres

Key

Figure 1. The location of the sampling site

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known as ‘Kalmi’ or ‘Kangkong’, were procured from the Bangladesh Agricultural Research Institute (BARI). Some 15–20 seeds of Ipomoea aquatica were sown in each pot after the stipulated time, and the pots were covered with an opaque plastic sheet to allow germination. When the germination was complete, in two to three days, the plastic was removed, and the plants were allowed to grow for 30 days. This is the time when it becomes comestible as a leafy vegetable. The pots were watered with As-free tap-water as and when required. Weeds were also removed manually.

Agriculture (USDA 1951) using augers, and spades and crowbars (for bulk samples). The collected soil samples were air-dried after visible roots and debris were removed. Some of the larger and massive aggregates were broken by gently crushing them with a wooden hammer, after which the ground samples were passed through a 0.5 mm stainless-steel sieve. The sieved samples were then mixed thoroughly to create a composite sample, and were preserved for laboratory analysis. The rest of the soil samples were crushed to smaller clods and passed through a 5 mm sieve. These soils were used for the pot experiment. Three different sources of organic matter, namely poultry litter, cow dung and sewage sludge, were used. The cow dung was collected from a dairy farm; the poultry litter from a chicken farm near Dhaka; and the sewage sludge was collected from the sewage treatment plant of Dhaka WASA. The organic materials were air-dried before they were applied to the pots.

Sampling

The plants from each pot were collected 30 days after germination. This was done manually by uprooting the plants carefully from the pot. The plants were washed first with tap water, then several times with distilled water to remove any soil adhering to the plant. Then the plants were separated into roots and shoots, and the fresh weight was measured. The samples were first airdried and then oven-dried at 70 ± 5ºC, and the dry weight was also taken. The oven-dried samples were ground and passed through a 0.2 mm sieve for further analysis. Soils from each pot were also collected and prepared for analysis, as mentioned earlier.

Experimental set-up

A pot experiment was set in the net house. Organic matter was applied at rates of 5 and 10 t/ha (the recommended application rates in Bangladesh (BARC 2005)), and there was also a control. The soil was spiked with arsenic at rates of 0, 20, 50 and 100 mg As/kg soil. Sodium meta arsenite (NaAsO2) was used as the source of arsenic. The spiking was done by thorough mixing of the required amount of salt with soil at the time of potting. All treatments were performed in triplicate. Clay pots with a 5 L capacity were used for the experiment, and the pots were arranged randomly in the net house. Every pot was filled with 5 kg of airdried soil. The soils had a pH of 7.08, organic carbon 0.91%, and had a of silty clay texture. The background As level in the soil was 1.6 mg/kg. This was taken as the control. There were a total of 84 pots (three treatments along with a control = 4); three replications = 3 (total, 4 × 3 = 12); three sources of organic matter = 3; two rates of application = 2 (total = 12 × 3 × 2 = 72); and 12 pots where no organic matter was applied; a sum total of 72 + 12 = 84 pots). The required amount of P, K, and one-third of the N doses (BARC 2005) were mixed with the soil. The sources of N, P and K were urea, triple superphosphate and muriate of potash respectively. The soils were kept moist for one week to allow the organic matter to mineralize and react with the spiked arsenic. Seeds of Ipomoea aquatica, locally

Laboratory analysis

Various physical and chemical properties of the soil samples and organic materials were analysed in the laboratory, following the procedures described by Imamul Huq and Alam (2005). Soil arsenic (both pre- and postexperiment) was extracted using aqua regia, while the arsenic in the plant and organic material was extracted using concentrated nitric acid (HNO3) (Portman and Riley 1964). The aqua regia/nitric acid digests were also used for determination of P, K and S. The total nitrogen of all the materials was determined by alkali distillation of the Kjeldahl digest; total P was determined spectrophotometrically by developing the vanadomolybdate yellow colour; K was determined by flame analyser; and the S was determined by turbidimetry using Tween-80. The arsenic in the extract was estimated by a hydride generation–atomic absorption spectrometer (HG–AAS), with the help of potassium iodide and urea, following calibration of the equipment. For every ten samples, a certified reference material (CRM) was included to ensure the QC/QA. Lead, cadmium and zinc content were determined by an

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Remediation of soil arsenic toxicity in Ipomoea aquatica, using various sources of organic matter

Table 1. Some properties of the organic matter (cow dung, poultry litter and sewage sludge) and the soil used in the experiment Properties

Cow dung

Poultry litter

Sewage sludge

Soil

Organic carbon (%)

15.40

17.60

4.95

0.91

Nitrogen (%)

1.86

2.23

0.38

0.13

Phosphorus (%)

6.97

6.82

2.77

0.03

Potassium (%)

0.38

0.58

0.68

0.41

Sulphur (%)

2.15

3.25

2.55

0.22

Arsenic (mg/kg)

1.85

1.55

1.66

3.29

Cadmium (mg/kg)

1.25

1.09

1.94

4.37

Lead (mg/kg)

1.10

1.45

1.15

69.08

Zinc (mg/kg)

1.13

1.23

2.36

7.46

Table 2. Fresh weight (g/pot) of total plants (values without parentheses are for the 5 t/ha applications, and those within parentheses are for the 10 t/ha organic-matter applications) Treatment (mg As/kg soil)

75.4 ± 2.7

83.6 ± 2.2 (99.0 ± 2.6)

88.7 ± 2.9 (114.9 ± 4.1)

136.8 ± 3.3 (146.0 ± 3.3)

73.4 ± 2.4

82.9 ± 1.8 (96.0 ± 2.6)

85.7 ± 2.9 (112.0 ± 3.1)

135.2 ± 3.0 (144.6 ± 4.1)

68.0 ± 1.7

78.6 ± 3.0 (84.4 ± 2.1)

83.0 ± 2.2 (107.3 ± 2.5)

129.7 ± 4.1 (139.3 ± 2.9)

100

61.0 ± 1.7

75.8 ± 2.2 (76.8 ± 2.1)

77.3 ± 2.5 (104.7 ± 3.3)

124.4 ± 4.2 (135.3 ± 4.2)

NM = no organic matter; CD = cow dung; PL = poultry litter; SS = sewage sludge

atomic absorption spectrometer (AAS) on the same digest as for As determination. Statistical analyses (ANOVA, regression and correlation) were carried out, using the MINITAB 13.0 package.

lowed the order: poultry litter > cow dung > sewage sludge. Moreover, with regard to the two rates of organic-matter addition, plants performed better in the 10 t/ha treated pots than in 5 t/ha treated pots. Vegetative growth

RESULTS AND DISCUSSION

Visual symptoms

The fresh weight of the plants per pot grown with different rates of As application, and with various sources and rates of organic-matter treatment, are shown in Table 2. The values presented in the table are the averages of three individual replications. The values in the table without parentheses, and within parentheses, are for 5 t/ha and 10 t/ha organic-matter applications, respectively.

Seed germination and plant growth were normal in all the pots, even at high doses (100 mg As/kg soil) of arsenic. Plant growth was better in organic-mattertreated pots than in the control pots. For the various sources of organic matter, the growth performance fol-

From Table 2 it is observed that the vegetative growth of the plants was suppressed due to the As spiking, irrespective of the rates and types of organic amendments. However, growth suppression was not significantly different to that seen for the control treat-

The collected organic-matter and soil samples used in the experiment were analysed in the laboratory before set-up of the experiment, in order to establish the nutrient content and some elemental properties, and the analytical values are shown in Table 1.

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ments. On the other hand, it is clear from Table 2 that the application of organic matter played a role in increasing the vegetative growth of Ipomoea aquatica. Out of the three different sources of organic matter, poultry litter made the best contribution, and the application rate of 5 t/ha of poultry litter produced a biomass more than 81% higher than the control treatments (no arsenic). Cow dung and sewage sludge increased the vegetative growth by about 18% and 11% respectively, for the same application rate. Not only that, but, at 20, 50 and 100 mg As/kg soil, the increases were 84%, 89% and 104%, respectively for poultry litter. The growth increase was even better at the 10 t/ha application rate. This could be due to the fact that the poultry litter contained more of the nutrients, particularly N and P, as compared to the other two sources. The growth increases seen for the 5 and 10 t/ha application rates were significantly different for cow dung and sewage sludge (p <0.001), but not for poultry litter.

spective of organic-matter treatment. In most cases, the roots accumulated more As than the shoots. This is a common phenomenon of As accumulation in nonphytoremediators (Ma et al. 2001; Imamul Huq et al. 2005; Hossain et al. 2006). It was observed that the 10 t/ha application rate performed better than the 5 t/ha rate in reducing As accumulation in the plant (p < 0.01). In this context, it could be ascertained that organic-matter addition is capable of reducing As accumulation in plants, more particularly the vegetable crop Ipomoea aquatica used in the present study. In Bangladesh, average soil As is close to 10 mg/kg, and, in soils irrigated with As-contaminated groundwater, this value stands at around 20 mg As/kg, with a few, much higher outliers (Imamul Huq et al. 2003). As such, the 20 mg As/kg soil treatment is considered here for further discussion. Arsenic accumulation in the whole Ipomoea aquatica plants grown in pots with arsenic-spiked soil and treated with different sources of organic matter at 5 t/ha and 10 t/ha, is shown in Figure 2. The application of organic matter at the rate of 5 t/ha reduced As accumulation in plants as follows: poultry manure – c. 48.0%; cow dung – c. 32.0%; and sewage sludge – c. 9.0%, compared to the control. By contrast, the application rate of 10 t/ha reduced the As accumulation in plants in the order: poultry manure – c. 77.0%; cow dung – c. 70.0%; and sewage sludge – more than 59.0%. The figures clearly show that when the application rate of organic matter was doubled, the reduction of As accumulation in plants for all types of organic sources was more than 55% (sewage sludge – 55.5%, cow dung – 55.8%, poultry litter – 55.2%). It is

Arsenic accumulation in plants

Arsenic accumulation in the roots and shoots of Ipomoea aquatica grown in arsenic-spiked soil and amended with different sources of organic matter at two different rates is shown in Table 3. The values presented in the table are averages of the three individual replicates. Values in the table without parentheses and within the parentheses are for 5 t/ha and 10 t/ha organic-matter applications, respectively. From Table 3 it is clear that the accumulation of arsenic in the roots and shoots of Ipomoea aquatica increased with increased As in the growth media, irre-

Table 3. Arsenic accumulation (mg/kg dm) in the roots and shoots of Ipomoea aquatica (the values without parentheses are for the 5 t/ha organic-matter application, and within parentheses are for the 10 t/ha application) NM

Treatment (mg As/kg soil)

Root

Shoot

Root

Shoot

Root

Shoot

Root

Shoot

4.6 ± 0.34

3.3 ± 0.46

3.5 ± 0.42 (4.3 ± 0.39)

3.3 ± 0.38 (4.0 ± 0.46)

4.3 ± 0.47 (3.0 ± 0.39)

4.6 ± 0.51 (2.5 ± 0.38)

2.8 ± 0.32 (2.2 ± 0.28)

2.1 ± 0.27 (0.5 ± 0.11)

28.7 ± 1.25

25.5 ± 1.15

25.5 ± 1.16 23.7 ± 1.08 (13.0 ± 0.74) (9.5 ± 0.96)

21.0 ± 1.08 (9.6 ± 0.87)

16.7 ± 0.87 (7.5 ± 0.61)

15.5 ± 0.98 (5.6 ± 0.56)

13.3 ± 0.31 (6.5 ± 0.26)

76.6 ± 1.96

59.0 ± 1.79

51.0 ± 2.01 46.5 ± 1.87 40.9 ± 2.07 32.9 ± 1.71 25.4 ± 1.27 21.7 ± 1.05 (41.0 ± 1.13) (36.3 ± 1.39) (30.3 ± 1.95) (27.2 ± 1.27) (15.4 ± 1.03) (10.1 ± 0.86)

100

101.1 ± 2.39 114.7 ± 2.44

59.3 ± 2.34 52.4 ± 2.47 45.3 ± 2.74 35.8 ± 1.47 28.2 ± 1.97 24.4 ± 1.27 (41.2 ± 1.42) (51.0 ± 2.72) (43.3 ± 2.54) (30.0 ± 1.54) (25.3 ± 1.78) (16.2 ± 0.97)

NM = no organic matter, CD = cow dung, PL = poultry litter, SS = sewage sludge

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Remediation of soil arsenic toxicity in Ipomoea aquatica, using various sources of organic matter

0 NM

10 t/ha

5 t/ha 10 t/ha

5 t/ha

10 t/ha

5 t/ha

No organic matter

20 No organic matter

Arsenic concentration (mg/kg)

Sources of organic matter NM = no organic matter; CD = cow dung; PL = poultry litter; SS = sewage sludge Figure 2. Arsenic accumulations in whole plants of Ipomoea aquatica at 20 mg As/kg treated soil and at two different rates of organic-matter application

phosphorus (Carbonell-Barrachina et al. 1994), and roots take up arsenic and phosphorus by the same mechanism (Meharg and Macnair 1990). Therefore, the chance of Asâ&#x20AC;&#x201C;P interaction could always be expected. The poultry litter contained much higher amounts of phosphate, and interestingly enough, the plants grown on the poultry-litter-treated soil also accumulated higher amounts of phosphate (data not shown in this paper). Therefore, it is assumed that the improved efficacy of the poultry litter in obviating As accumulation in Ipomoea aquatica could be attributed both to a greater methylation reaction and to greater Asâ&#x20AC;&#x201C;P interactions. Our findings corroborate the observations of Kabata-Pendias and Pendias (1985), who found that arsenic is less toxic when the plant is well supplied with phosphorus, as well as the observation by Pais and Jones (1997) that the phytotoxicity of arsenic is reduced with high phosphorus availability. The results of the present study are also consistent with the work by Shiralipour et al. (2002), who observed that compost has the ability to hold As in the exchange sites, making it less available to plants. High As accumulation in roots and shoots of Ipomoea aquatica at high As levels in soil could be attributed to the higher phytoavailability of the element. This has been reported for this plant, as well as others (Farid et al.

interesting to note here that the addition of organic matter, while reducing the As accumulation in the plant, also caused a reduction in the accumulation of the heavy metals Cd, Pb and Zn. There was significant correlations between As and these elements in plants (p values are 0.028, 0.003 and 0.001 for Cd, Pb and Zn respectively). Thus, organic-matter addition can, not only alleviate As accumulation, but it can also alleviate heavy-metal toxicity in the food chain. Soil humic acids are active in retaining As(III) and As(V) through adsorption. The methylation reactions of arsenic may decrease the toxicity of As by decreasing its mobility in soil. When an element is less mobile, its uptake by plants is also lower (Suzuki 2002). In the present case, the As accumulation in the plants for the different organic-matter treatments was in the order: poultry manure < cow dung < sewage sludge, and this corresponded to the carbon content of the organic sources. The higher the carbon content of the organic source, the lower was the As accumulation in plants treated with that source. This could be related to a higher methylation rate in the presence of the respective organic sources. Wastewater, sewage sludge and refuse composts have an effect on the accumulation and movement of arsenic in cultivated soil (Azcue and Nriagu 1994). Arsenic is chemically similar to

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2003; Imamul Huq et al. 2006a; Sanyal et al. 2007). Our findings also indicate that, even at high soil arsenic levels, the addition of organic matter – specifically, poultry litter, could be a strategy to remediate As accumulation in growing crops. The fraction of As reacting with P and methylating needs to be assessed further. Using organic waste, particularly poultry manure and cow dung, in agriculture could raise the issue of the spreading of avian flu and cow-related diseases. This possibility is remote in Bangladesh, as both poultry litter and cow dung are sun-dried before application to soil, and the avian virus is destroyed at high temperatures. As for cow-related diseases, there is no mad cow disease problem in Bangladesh. Foot-and-mouth disease is well contained and not very widespread.

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ACKNOWLEDGEMENTS

The authors acknowledge the technical support of Ms Sultana Parvin of BACER-DU during the sample analyses, and Mr A.F.M. Manzurul Hoque of SRDI for his help in drawing the sampling site map.

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Sanyal, S.K., Dutta, P., Das, S., Bose, A., Mondal, N., Bose, P., Pal, S., Kole, S.C., Bandyopadhyay, P., Mondal, S. and Bhattacharyya, S. (2007) An investigation into accumulation of arsenic in biological systems of the agro-ecology of the Nonaghata area of Nadia, West Bengal. In: Proc. Int. Workshop on Arsenic Sourcing and Mobilisation in Holocene Deltas (Basu, B. ed.), pp. 99–100. School of Fundamental Research, Kolkata, India

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Imamul Huq, S.M., Islam, M.S., Joardar, J.C. and Khan, T.H. (2006c) Retention of some environmental pollutants (As, Pb and Cd) in soil and subsequent uptake of these by plants (Ipomoea aquatica). Bangladesh J. Agric. and Environ., 2 (1), 61–68

Shiralipour, A.L., Ma, Q. and Cao, R.X. (2002) Effects of Compost on Arsenic Leachability in Soils and Arsenic Uptake by a Fern. State University System of Florida, Report No. 02-04. Florida Center for Solid and Hazardous Waste Management, University of Florida, Gainesville

Imamul Huq, S.M., Shila, U.K. and Joardar, J.C. (2006d) Arsenic mitigation strategy for rice by water regime management. Land Contamination & Reclamation, 14 (4), 805– 813

Sikder, T., Joardar, J.C. and Imamul Huq, S.M. (2007) Sewage sludge as soil ameliorator. Bangladesh J. Agric. and Environ., 3 (1), 63–73

Imamul Huq, S.M., Abdullah, M.B. and Joardar, J.C. (2007) Bioremediation of arsenic toxicity by algae in rice culture. Land Contamination & Reclamation, 15 (3), 327–333 Joardar, J.C., Rashid, M.H. and Imamul Huq, S.M. (2005) Adsorption of arsenic (As) in soils and in their clay fraction. Dhaka Univ. J. Biol. Sci., 14 (1), 51–61

Suzuki, K.T. (2002) A speciation study focused on the identification of proximate toxic arsenic metabolites. In: Proc. of the UNU–NIES Int. Workshop on Arsenic Contamination in Groundwater – Technical and Policy Dimensions, Tokyo, Japan

Kabata-Pendias, A. and Pendias, H. (1985) Trace Elements in Soils and Plants. CRC Press Inc., Boca Raton, Florida. 315 pp.

United Nations Development Program and Food and Agriculture Organization of the UN (1988) Land Resources Appraisal of Bangladesh for Agricultural Development. Agroecological regions of Bangladesh. Report 2. 570 pp.

Kwiatkowska, J. and Maciejewska, A. (2006) The effect of organic materials on the uptake of heavy metals by maize (Zea mays) in heavy metals polluted soil. 18th World Congress of Soil Science. Philadelphia, Pennsylvania

USDA (United States Department of Agriculture) (1951) Soil Survey Manual. Soil Survey Staff, Bureau of Plant Industry, Soils, and Agricultural Engineering, United States Department of Agriculture, Washington. 503 pp.

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DOI 10.2462/09670513.904

Cover systems for landfills and brownfields Georg Heerten and Robert M. Koerner

Abstract Some 25 to 30 years after Western nations, the emerging economies in Asia and South America, as well as the countries of the former Soviet Union now have to address the environmental problems of waste management, and to establish long-term safe landfills as a first step towards a waste management regime governed by recycling and waste-stream reduction. A cover system as part of the landfill design should permanently prevent the uncontrolled release of landfill gas (primarily methane gas (CH4)) and pollutants, as well as the infiltration of precipitation water into the body of the landfill. Active degassing of municipal landfills takes on particular significance in the light of current climateprotection objectives, and can also provide energy by utilizing the captured gases. This paper describes current problems with classic compacted clay liners (CCLs) and their still unquestioned use in landfill legislation and landfill construction around the world. This paper focuses on dehydration/desiccation and deformation cracking when CCLs are used in landfill-capping applications. As alternative solutions, it is shown that modern capping design using geosynthetics such as certified geomembranes and certified geosynthetic clay liners (GCLs) are more than ‘equivalent’, and have proven to give better long-term, reliable solutions. The authors recommend the replacement of CCLs by certified geosynthetic components such as geomembranes and GCLs. Key words: clay cracking, compacted clay liners, durability, field performance, final covers, landfills

INTRODUCTION

High population densities and a high degree of industrialization, in combination with lifestyles that have detrimental effects on the environment, for example in the US and in Germany, led comparatively early (about 30 years ago) to organized waste disposal at landfills designed with base and surface seals. Prior to this, of course, garbage was collected but mostly deposited unsorted in old sand or gravel pits, in stone quarries or on soil having minimal permeability – frequently in the vicinity of residential areas – without a base seal. Modern landfills, both during their active operation and after closure, should be isolated by a combination of sealing systems and contamination barriers to restrict their adverse effects on the environment to an acceptable level. Surface sealing systems should permanently Received June 2008; accepted September 2008 Authors Prof. Dr.-Ing. Georg Heerten, RWTH Aachen, Germany Prof. Robert M. Koerner, Ph.D., P.E., NAE, Geosynthetic Institute (GSI), Folsom, PA, USA

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prevent the uncontrolled release of landfill gas (primarily methane gas (CH4)) and pollutants, as well as the infiltration of precipitation water into the body of the landfill. Active degassing of municipal landfills takes on particular significance in the light of current climateprotection objectives. This is because the combustion of collected methane gas in internal combustion engines or simply by flaring it (i.e. open flame burn-off) contribute significantly to climate protection, as methane gas is about 20 times as detrimental as carbon dioxide (CO2). Currently, many societies and countries around the world are forced to pay the price of population explosion and industrialization, in the form of rapidly rising environmental stress. They too must now define comparable disposal paths for their industrial waste, household garbage and inert waste materials. With a delay of about 25 to 30 years, emerging economies in Asia and South America, as well as the countries of the former Soviet Union (which have comparable environmental problems) are going through this development without utilizing or conforming to the body of expertise that has

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

Figure 1. Large landfill in a residential area of a large Asian city in 2006

been gathered over the past 30 years in countries such as the US or Germany.

sealing systems must be made transparent in order to make the case for economically and ecologically superior solutions, thereby avoiding a repetition of negative experiences. As will be presented in more detail, this is particularly true of the unquestioned use of classic compacted clay liners (CCLs) as the sealing element in surface sealing systems.

An example of this, in 2006, was the large landfill in a residential area of a major Asian city shown in Figure 1. This is an example of the serious detrimental effects on groundwater and the atmosphere that are produced by the absence of a base seal. Severe damage and contamination to air, land and water as a consequence of population growth and ongoing industrialization are the compelling reasons for developing and implementing appropriate environmental practices with correspondingly large economic overheads. The mind-set and general acceptance of active garbage collection and safe disposal is still to be cultivated in these societies. Even though, for example, the European Union has adopted environmental goals to prevent waste and recycle waste in tightly closed material streams so that landfilling can be made an obsolete concept, economic development politics should not forget that societies must make their way through all stages of development along the path from uncontrolled dumping to closed material streams. Thus, support in many of these emerging markets for waste logistics and orderly, secure landfill practices must have top priority as a first step toward more sophisticated, and much more expensive, environmentally prudent goals. In this phase, the objective is to bolster development in waste-disposal and landfill engineering by making available the expertise gained over decades in countries like the US and Germany. Even the now-recognized potential hazards associated with the long-term effectiveness of landfill

2. A GLOBAL COMPARISON OF COVER SYSTEMS 2.1

Cover systems in current national legislation

About 25 years ago, the first national guidelines, ordinances and regulations were introduced in the US and Germany for controlled (well-regulated) waste disposal in landfills. These introduced binding requirements for landfill base sealing and cover systems. The core elements of the sealing systems were mineral components, clay as the classic sealing layer, and gravel or sand as the seepage water and gas drainage layers. When, in 1999, the Geosynthetic Research Institute (GRI) carried out the first worldwide survey of landfill liner and cover systems,13 37 countries or federal states had already established regulations for landfill sealing systems. The requirements were often different for hazardous waste landfills, municipal landfills and construction material dumps. All of these guidelines and regulations were basically â&#x20AC;&#x2DC;carbon copiesâ&#x20AC;&#x2122; of then-progressive pioneering efforts, and concentrated on mineral solutions for their sealing systems, employing clay, gravel or sand layers for the aforemen-

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tioned tasks, sometimes with variations in permeability requirements or layer thicknesses. Almost ten years later, in 2007, in a second worldwide survey of landfill base and surface sealing systems,16 the number of nations with landfill regulations covered by the study had grown to 52 countries – an increase of about 40%. The USEPA, followed by most countries, had three unrestricted components which were found to be predominant as sealing system elements:

for the landfill regulations of individual US states, which must first comply with the super-ordinate regulations of the USEPA but go beyond these basic rules by expressly specifying geomembranes and geosynthetic clay liners (GCL), as well as geodrains or other geosynthetic drain structures for the design of landfill base and cover systems. This situation in US states, seemingly decoupled from the rest of the world, is justified by virtue of documented economic, ecological and functional advantages. For example, it has been

• the CCL; • the geomembrane; and • the sand drainage layer.

explicitly documented for seepage water control systems implemented in the US, that a composite liner system of geomembrane and geosynthetic clay liner exhibits far less seepage water volume than do other

Thus, the initial guidelines gained wider acceptance. Combination seals of CCLs and geomembranes (HDPE) were required, particularly at the landfill base for hazardous waste and municipal waste landfills, but also as landfill covers for hazardous-waste landfills. In 23% of the regulations reviewed there was no prescribed method of sealing a landfill’s surface; in 65% of the regulations, a classic compacted clay liner was perceived as sufficient; and in only 8% of the regulations was a composite liner system required to be made from CCL and HDPE geomembranes. Thus, 73% of the regulations state that a classic clay liner for the landfill surface should be provided, i.e. three out of four landfills should have a classic clay liner. Even in separate reviews of individual US states, which must at least conform to EPA requirements for sealing systems, the current situation is that they all more-or-less exclusively rely on the long-term effectiveness of a classic clay or fine-grained sealing layer for the final surface seal on municipal landfills. From the standpoint of the authors and many expert colleagues, this is a surprising situation – particularly in view of the further points made below. This situation calls for global, rigorous corrective action. 2.2

system structures under otherwise comparable conditions. Beyond this situation in the US, international practice for landfill construction is to plan and execute such ‘equivalent’ solutions, for the most part as standard solutions prescribed by governmental agencies. Aside from the standard practice of using a geomembrane over composite liner systems (almost exclusively HDPE – currently about 150 million m2/year), there are currently about 40 million m2 of geosynthetic clay liners and about 75 million m2 of geodrain systems being incorporated into landfill sealing systems around the world each year. Thus, practical execution differs quite markedly from governmental minimum requirements, with the result that geosynthetics now very clearly characterize actual engineering practices for the sealing systems of hundreds of landfills around the globe. Whereas these standard systems and their mineral components, as envisioned by governmental agencies, are simply presupposed and expected to have longterm effectiveness without any further evidence; the so-called ‘equivalent’ geosynthetic system components are typically subjected to comprehensive testing

Surface seals in practical implementation

to prove their long-term effectiveness – from today’s

Due to the uncritical transfer of mineral capping solutions from the regulations in one country to those in others, as well as in the super-ordinate stipulations of the USEPA, alternative system components or sealing systems are not even mentioned or, at best, only implied by statements that ‘equivalent’ systems or system components, may also be used. This is not the case

perspective a totally inequitable treatment of alternative sealing systems. After over 30 years of unjustified faith in the long-term effectiveness of classic clay sealing systems, there is still no proof concept for this material, as there has long been in the case of geosynthetics.

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to roots and as a safeguard against dehydration of the mineral clay sealing layer) cannot be perceived as a composite liner system because, in this case, the two sealing components are not independent of one another, but rather complement one another in order to accomplish the sealing effect.11

3. COMMENTARY ON THE LONG-TERM EFFECTIVENESS OF CCLS IN SURFACE SEALING SYSTEMS 3.1

General

CCLs have long been used as hydraulic barriers or seals in canals, dams, retaining basins and other structures in direct contact with water. Extensive geoengineering and geological literature is available on classic clay liners. Therefore it is only natural that one would consider using a CCL as a seal beneath a body of waste where seepage water is to be trapped. In the opinion of the authors, this is entirely justifiable for landfill sealings when a fine-grained soil is economically available; when the clay layer can maintain the stability of its water content over the long term without problems; and when it is installed on a solid foundation of subsoil where settlement is minimal or non-existent. However, the use of a classic clay liner over a body of waste (i.e. in the cover or surface seal of a landfill) is a major challenge in view of the long-term sealing effect for critical water-content parameters of the clay liner, and the uneven settlement and subsidence associated with the body of waste.

Since the standard system has long been a ‘legally fixed constant’, there are no specific investigative techniques available to evaluate the long-term effectiveness of composite liner systems in surface sealing systems. With the information currently available, it therefore follows that the standard sealing (as it stands in current administrative regulations) should be eliminated when formulating new integrated landfill regulations, as is currently the case in Germany. Existing proof concepts have been demonstrated at Georgswerder in Germany and Sigmundskron/Bozen in Austria;4 for example, an accompanying long-term test-field/lysimeter investigation of the mineral components in a composite liner system without the protective effect of an overlying geomembrane, in order to provide the multi-year monitoring data that would produce firm conclusions about the long-term effectiveness of the mineral sealing components. Although carried out at comparatively high temperatures in the waste body of a mono-landfill, five years of monitoring the test-fields of moderately plastic clay at the Sigmundskron/Bozen landfill, both with and without a protective geomembrane, revealed dehydration damage, with crack formation in the moderately plastic clay layer. Cracks in the test-fields without a geomembrane had reached a semi-permanent state, with the shrinkage cracks within the layer having widths of up to 4.5 mm.4 Concomitant to this there was a seven-year monitoring programme of mixed-grain mineral sealings that revealed no comparable degradation. However, extrapolation options for the corresponding results in mineral-system components still need to be developed in order to draw conclusions about the long-term effectiveness of these methods.

Thus, the text which follows will deal with questions arising from current realities in Germany and the US with respect to whether or not a classic clay liner used as a landfill surface seal is at all able to fulfil its assigned function over the long term. 3.2

3.2.1

Increased permeability due to dehydration

Experience in Germany

Investigations of sealing systems with lysimeters, test fields and excavations have reported repeatedly on the danger to, or loss of, the sealing effect of mineral sealings6,7,8,9 which renders questionable the original concept for standard sealings, designed as a composite liner system. The standard system is based on the assumption that, as a convection barrier, the geomembrane is characterized by limited long-term effectiveness, and that, subsequently, the 50-cm-thick clay liner will take over the sealing effect on a permanent basis. This technical solution has been discarded, since it has become known that the clay liner can lose its sealing effect within only a few years of dehydration, and thus is not a truly long-term solution.

On the subject of ‘Anforderungen an DeponieOberflächenabdichtungssysteme’ [demands made on landfill surface sealing systems], participants in a status workshop arranged by Working Group 6.1. ‘Geotechnik der Deponiebauwerke’ [geotechnics in landfill structures] of the Deutsche Gesellschaft für Geotechnik (DGGT) [German Geotechnical Society] and the Höxter department for waste management and landfill

A sealing system in which a geomembrane is necessary to protect another sealing element (e.g. as a barrier

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over the long term, i.e. not significantly longer than the functional lifespan of the geomembrane. This is because the mineral components, in the form of a mineral clay sealing layer with a high percentage of finegrained material, become susceptible to shrinkage cracks and dehydration.

engineering at the Lippe and Höxter Polytechnic University, came to the following conclusions in December 2006.21 The standard sealing system for Class I landfills in Germany (building-rubble landfills) is a surface sealing system with only a classic, mineral clay sealing component. Scientific investigations and experience over recent decades have shown that the effectiveness of this clay-mineral sealing layer can be endangered by the following:

This critical evaluation of the ‘standard sealing system’ for landfills of Class II and III (municipal waste and hazardous waste landfills) was thoroughly endorsed by the participants of the status workshop. Thus, the geomembrane becomes the decisive element for long-term effectiveness. A composite liner system made of geomembrane and classic clay sealing renders the classic clay sealing superfluous.

• Rising capillary water, convective water vapour transport and root penetration can lead to dehydration of the mineral sealing, with the potential for the formation of irreversible desiccation cracking, which would make the sealing ineffective over the long term.

3.2.2

Experience in the US

There are also reports from the US of clay seal failure scenarios as a result of changes in water content. It has been determined that, even in regions with a cool/humid climate, critical dehydration of CCLs can take place in the summer months, and that frost can also have a damaging effect.

It should be noted that, to date, no design rules for surface sealing systems exist that are proven to eliminate desiccation cracking in a clay-mineral sealing, or which describe how a respective system structure for sealing systems could be conceptualized to prevent the occurrence of unacceptable water-content fluctuations. According to the original concept underlying German landfill regulations for composite liner systems, the mineral sealing component’s initial function in the composite is to limit water penetration of any small imperfections in the geomembrane. Over the long term (a period >> 100 years), the mineral sealing component should provide the permanent sealing function. However, along with the failure of the geomembrane, the root barrier function is also lost, thus the mineral component might then be exposed to the same influences as a single mineral sealing layer in the standard system for Class I landfills.11 While the mineral sealing components are shielded against water intrusion by a functional geomembrane, there is also a risk of water extraction as a result of temperature-induced water migration. For primarily downward-oriented temperature gradients (i.e. where sealing components at the landfill’s surface are warmer than the landfill’s body) medium- to long-term dry-cracks can occur. Henken-Mellies11 come to the conclusion that composite liner systems, as they have been specified in Germany’s standard sealing system, are not suitable for preventing water from seeping into the landfill’s body

Over the past 15 to 20 years, there have been various studies to research the performance of CCLs in landfill surface sealings. These studies employed various sizes of lysimeter beneath the CCLs, in order to collect and measure the seepage water penetrating the CCL. It should be noted that the generally accepted maximum permeability coefficient of the CCL is k < 1 × 10–7 cm/s, and that the corresponding conversion to 32 mm/year of seepage is important for the use and evaluation of field lysimeters. Albright et al.1 provide a good overview of the investigations performed in three different climatic environments in the United States: cold/humid, warm/humid and semi-arid. It has been reported that the CCL only functions acceptably in the two semi-arid locations, with a seepage rate of less than 32 mm/year. This may be due to the initially minimal precipitation rates of only 140 to 300 mm at the semiarid locations. In all other regions the seepage rate for the CCL was greater than 32 mm/year, and in some cases it was substantially greater. In some cases, samples were taken and the actual permeability coefficient was assessed in the laboratory, revealing increases as high as four orders of magnitude. A separate study carried out by the Maine Department of Environmental Protection found similar values when using an on-site

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test method for measuring the actual permeability of the CCL in the field.

surface sealing systems, there is an urgent need to develop a proof strategy from which suitable system structures and material choices can be derived for permanently effective clay liners. A requirement calling for lysimeter fields (that would be operated for a minimum period of ten years) as a mandatory constituent of surface sealings that contain classic clay liner components, could provide the basis for rapid dissemination of data about clay-liner dehydration security or endangerment. Despite this measure, however, the second major potential for endangering the permanent effectiveness of classic clay liners, namely forced deformation caused by irregular settlement and subsidence of the body of the landfill, would still have to be monitored separately.

In the same study, Albright et al.1 evaluated the performance of three CCLs in landfill surface sealings. This study concentrated entirely on changes to the permeability coefficient, by means of laboratory permeability tests, made on samples taken that had been buried for four years. Here too, the permeability coefficients had increased substantially, with values of k = 3.6 × 10–5 cm/s, 1.3 × 10–5 cm/s and 3.9 × 10–6 cm/s, whereas the required value is k < 1.0 × 10–7 cm/s. The most recent example is reported by Albright et in the case of a CCL in a final surface sealing in southern Georgia. Following a four-year service period, the permeability coefficient had risen from about 1 × 10–7 to 1 × 10–4 cm/s.

al.2

There are a number of reports from the United States, with many examples, in which a clay sealing layer initially met requirements (k < 1 × 10–7 cm/s), but after only a few years of service exhibited significantly increased water permeability rates as a result of dehydration processes and accompanying crack formation – with measured permeability coefficients reaching 10–4 to 10–5 cm/s (10–6 to 10–7 m/s).

4. RISKS TO SEALING EFFECTIVENESS CAUSED BY IRREGULAR SETTLEMENT AND SUBSIDENCE 4.1

General

Mineral sealing layers are particularly sensitive to various types of settlement and subsidence in the body of a landfill. The forced deformation in the surface sealing system, combined with surface seal crack-formation and dehydration, can lead to increased system permeability beyond tolerable limits. Even while the landfill is still in operation, the regular measurement of landfill body settlement can provide a basis for the prognosis of residual deformation, which can be anticipated when temporary or final surface sealings are applied. This permits an estimate of the stress magnitudes, which are to be borne by the projected sealing elements. A proof is recommended as the criterion for clay liner compatibility, such as that proposed by GDA Recommendation E2-13,5 which evaluates the anticipated deformation of the mineral sealing system’s surfaces (top or bottom of layer) against its elongation at break value for the sealing material to be used. Witt23 has proposed that in the future the sealing material’s water permeability should be determined directly on laboratory samples with an axial elongation of ε = 2‰. This proposal not only confirms an existing deficiency in the assessment strategy for the permanent sealing effectiveness of classic clay liners as a component in landfill surface sealing systems, but is also an important indication of the very strict limitation on clay liner deformation at ε = 2‰ (0.2%). This value must be

This establishes that, independently of differences in the overall design of sealing systems, surface sealing systems with classic clay liners and superimposed drainage layer and re-cultivation layers of up to 1.5 m thickness are insufficient to prevent substantial increases in the clay liner’s permeability to k values of 10–4/10–5 cm/s or 10–6/10–7 m/s. A geomembrane integrated as a second sealing element and component of a composite liner system can delay this development, above all by providing longterm active protection from root penetration. However, the long-term effectiveness of the composite liner system is only ensured by the geomembrane. Thus, a classic clay liner according to current concepts of landfill surface sealing systems as described here, is entirely superfluous, because it only provides permanent effectiveness in conjunction with a geomembrane which already provides this protection. The selection and installation of the geomembrane is therefore of decisive significance for the permanent effectiveness of the sealing system. Should the regulatory authorities and landfill operators wish to continue to employ classic clay liners in

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Table 1. Data on tensile strain at failure for compacted clay17 Type or source of soil

w * (%)

P.I. ** (%)

εf *** (%)

Clayey soil

19.9

0.80

Illite

31.4

0.84

Kaolinite

37.6

0.16

Anonymous Dam

16.3

0.14

Rector Creek Dam

19.8

0.10

Woodcrest Dam

10.2

n/n

0.18

Wheel Oil Dam

11.2

n/p

0.07

Willard Embankment

16.4

0.20

Ave. = 0.31%

* Water content ** Plasticity index *** Tensile elongation at failure

observed, particularly for all landfill surface sealings over municipal waste and the long periods of largescale settlement and the resulting surface deformation.

A surface sealing system with the following components was completed in 1990: • 150 mm of topsoil;

4.2

The compatibility of landfill deformation with

• 450 mm cover soil;

tolerable elongation of classic clay liners

• 300 mm sand drainage layer;

Even though settlement in a waste body comprising municipal waste may be as great as 30% of its initial depth (depending on the waste’s composition, the manner in which the waste is deposited, the fill depth, the water situation and the age of the deposits), several examples are available in the literature which establish the critical deformation limits of classic clay liners with respect to their permanent sealing effectiveness. The problem is less associated with the overall even settlement of the waste body than it is with local, closely limited differences in settlement and subsidence. In the US, there are many documented, proven cases of critical differential settlement and subsidence of landfills that exhibit acceptable limits – among others, landfills in New Jersey, Pennsylvania, Florida and Ohio (Koerner 2003). Current measurements at the landfill in New Jersey have revealed that there is differential settlement and subsidence at the surface. The 25hectare (61.78-acre) landfill was in operation from 1966 to 1981. It was filled with municipal waste, plant waste, commercial waste and small amounts of dry, treated sewage-sludge. Probably this material was used to fill an old quarry with an unknown depth of waste – a typical old landfill without a base seal, like many others of its kind that can be found around the world and which, in some cases, unfortunately, are still in operation today.

• 300 mm compacted clay liner; • 300 mm cover soil; • about 450 mm levelling layer; • waste body. Seven years after installing the surface sealing, and 16 years after dumping ceased, the landfill’s surface appearance was characterized by seven different settlements and subsidence areas. The valleys and craters were measured individually. The approximation equations specified by Koerner15 were used to calculate the deformation relevant to the clay sealing layer. The deformation profiles and maximum elongation values for the surface seal are illustrated in Figure 2. The calculated deformation in the sealing system varies from 1.8 to 27.4%, and thus lies magnitudes beyond the permissible elongation, at break values published in the literature for individual soils and clays and for dam construction17 (Table 1). In the vicinity of the measured and calculated deformation, it can certainly be assumed that the installed 300-mm-thick compacted clay liner has widely lost its sealing effectiveness due to the deformation cracks, perhaps aggravated further by dehydration. Frequently a seal failure is also indicated by visible disturbances in plant growth (Figure 3).

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Figure 2. Contours of local settlement and subsidence in a New Jersey landfill, with the calculated maximum elongations in the surface seal system

Lehners18 describes the necessary long-term strategy to derive prognosis values for residual settling from settlement measurements taken during a landfillâ&#x20AC;&#x2122;s utilization. These values can then be used to design an intermediate cover layer and/or final surface sealing for a landfill.

The situation described here is unfortunately typical of many old landfills predominantly filled with untreated residential waste: i.e. with no base seal at all, and only a classic compacted clay liner or just a soil cover over the landfillâ&#x20AC;&#x2122;s surface. These practices are still current in the emerging economies.

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Figure 3. Visible disturbances in plant growth indicate a seal failure

At the Damsdorf landfill in northern Germany, it was possible to wait for landfill body deformation and settlement to take place or to control it in such a manner that the permissible elongation of the stiff boulder clay (ε = 2.5‰ (0.25%)) employed there would not be exceeded, and furthermore that anticipated vertical deformations, of the order of 3 to 5% of waste depth, would not lead to deformation-related damage to the sealing.

5. ALTERNATIVE SOLUTIONS WITH GEOSYNTHETICS 5.1

General

Whereas the mineral components of a landfill’s sealing system for sealing or drainage as defined in regulations (e.g. layer thickness, permeability, grain sizes, calcium content) and which are in compliance with installation criteria (e.g. density, water content) are built and constructed to a high standard, their actual long-term effectiveness and stability after installation is simply presupposed and accepted without any proof – frequently based on the grain material’s long-term stability.

Lehners18 recommends: • the measurement of the deformation already occurring during landfill operation, in order to obtain initial values for the design of a surface seal;

However, long-term stability is not equivalent to long-term effectiveness. A component that is effective in the long term is, however, necessarily also stable for this period of time. A myriad of interactive effects and influences can make a long-term stable component ineffective for its planned task in a landfill sealing system. There are various so-called ‘mineralogical analogies’, which may allow judgements to be made about the long-term stability of mineral substances (e.g. quartz grains), but these are certainly not valid for judgements about the long-term effectiveness of geotechnical structures made of materials such as gravel, sand, clays or their mixtures, with and without additives to improve certain characteristics.

• the control of deformation by waste selection or sorting, and the managed deposition of waste at the site; • the repositioning of waste deposits if this is necessary to help reduce future deformation; • the monitoring and evaluation of surface deformation with line profiles in order to monitor the stress on the surface seal. An appropriate strategy can at least prevent deformation-related damage to classic clay liners in surface sealing systems. However, the potential damage that can be caused by changes in water content or dehydration remains unrestricted.

Evidential proof of long-term effectiveness in sealing systems will be dealt with in the text that follows.

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This treatment will draw on alternative geosynthetic components as a measure for comparison, because the experience of recent years has shown that there are no other system components whose suitability has been internationally compared, intensively discussed, researched, reviewed and proven. The minimal knowledge about the long-term effectiveness of mineral layers has led, paradoxically, to their greater acceptance, rather than geosynthetic components, despite the greater body of knowledge that exists about them. 5.2

Supplementary proof of the stability of landfill embankments must be documented separately. This should be done with state-of-the-art techniques for assessed friction coefficients between the geomembrane and adjacent friction parameters, with sufficient safety factors for the structural and operational conditions of the specific product. The inspection of surface seals (as reported by Rödel22) which employ BAM-approved geomembranes is carried out in Germany using electrical leak detection systems. These inspections are to establish that there is less than one damaged location per 50 000 m2 of GM liner material. The causes of the defects found were about equally divided between construction activity associated with the installation of overlying mineral layers and with faults in the welding of the geomembrane. Thus, more than 100 000 m2 of this material are properly welded, and more than 100 000 m2 are properly installed and covered (earthworks) without any defects – impressive evidence for the high quality that can be achieved with a sealing made of HDPE geomembranes. It can be assumed that under these documented boundary conditions, the sealing objectives, i.e. the prevention of uncontrolled release of landfill gas and hazardous materials into the environment, as well as prevention of precipitation water from intruding into the landfill body, are optimally achieved on a long-term basis. Therefore BAMapproved or GM13-tested geomembranes can now serve as the standard against which all other sealing components are measured (even though BAM approval demands markedly stricter requirements). This assessment is supported by investigations and conclusions in the international literature.

Proof of the long-term effectiveness of

geosynthetics

5.2.1

Geomembranes (GM)

HDPE geomembranes have been preferred as sealing elements in landfill construction for about the past 35 years, due to their superior chemical stability. They are almost exclusively a constituent of composite liner systems, as specified in national regulations. The approval procedure for HDPE geomembranes was introduced by the Berlin-based Bundesanstalt für Materialforschung und -prüfung (BAM) [Federal Institute for Materials Research and Testing] at the end of 1989. This procedure has now been used in Germany for almost 20 years to evaluate the permanent functionality of geomembranes as a landfill sealing component. In the US, the regulatory requirements are defined by the GRI (Geosynthetic Research Institute) Test Method GM13 – ‘Test Methods, Properties and Testing Frequency for High-Density Polyethylene (HDPE) Smooth and Textured Geomembranes’. The following supplementary factors should be noted when using BAM or GRI-Standard approved or tested geomembranes in a surface sealing system:

There is currently an extensive literature base regarding the long-term effectiveness of HDPE geomembranes20 which is based on time-temperature superposition followed by Arrhenius modelling (Koerner and Hsuan14 and Müller20) (Table 2).

• the superimposed layers (drainage and cover) offer perfect long-term protection against UV radiation; • the geomembrane is able to withstand a large range of forced deformation without damage; • the geomembrane remains impervious to the effects of frost, fluctuations in water content or water tension in the overlying layers (e.g. cover soil and topsoil layers);

The material’s definitive mechanical characteristics will be degraded over the specified timeframe. These are conclusions derived from aggressive laboratory immersion tests conducted at 80°C, in order to accelerate the ageing processes at a constant temperature. According to Table 2, at a given constant ambient temperature for the geomembrane, for example 30°C, the mechanical characteristics will have degraded over a

• the geomembrane is a stable barrier against roots and rodents; • the geomembrane remains permanently water- and gas-tight.

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LAGA-Adhoc-Gruppe ‘Deponietechnische Vollzugsfragen’ [LAGA ad hoc group for landfill engineering implementation questions] to the Ausschuss für abfalltechnische Fragen (ATA) [committee for waste engineering questions] of the Länderarbeitsgemeinschaft Abfall (LAGA) [states’ working group for waste] with a recommendation for approval of their use as mineral sealing components in landfill surface sealing systems (DK I) [landfill class I] and indicated that their use could be expanded to DK II [landfill class II] providing that two additional proofs are successfully completed.

Table 2. Long-term effectiveness of HDPE geomembranes in conjunction with ambient temperature Temperature (°C)

Long-term effectiveness (years)

400–1000

250–600

150–400

100–250

60–180

period of 150 to 400 years, to the point at which only a brittle synthetic plate remains, which, however, does still fulfil its sealing function. This timeframe is denoted in the literature20 as the ‘service life’, and is therefore the sought-after long-term effectiveness of the by-then brittle HDPE plate that still has its sealing effect intact. At the end of this period it will be lying on a stable landfill body that has long since ceased to require ‘post-operative’ care, but which continues to fulfil its sealing function. Even with somewhat different proof techniques, this fundamental claim for BAMapproved or GM13-tested HDPE geomembranes can be made. Corresponding quality assurance systems can guarantee the long-term effectiveness of sealing systems anywhere in the world. 5.2.2

German government representatives in the LAGAAdhoc-Gruppe have thus accepted the proofs of permanent stability and permanent sealing effects for these products. This followed a multi-year proof procedure that was able to build on the foundation of test results and appraisals in an earlier approval issued by the Deutsches Institut für Bautechnik (DIBt) [German institute for construction engineering]. BAM was able to prove a permanent shear-force transfer after developing and performing appropriate long-term shear/creep tests.19 In 2004, it was possible to present a BAM test report on the long-term shear strength of a bentonite mat, documenting the extrapolated functional longevity at a 15°C ambient temperature for a period of over 400 years.

Geosynthetic clay liners (GCL)

Several samples from this long-term series were subsequently examined for residual internal shear strength in short-term experiments. The samples used in these BAM experiments had been artificially aged for the equivalent of hundreds of years, yet still exhibited substantial load-carrying reserves.12 In summary, the results show that, when used in landfill surface seals, the internal shear strength of the geosynthetic components alone, in the bentonite mats investigated, is sufficient to ensure the structural stability of the sealing system over at least centuries (>>100 years), whereby these current testing methods are unable to establish a definitive limit on the functional lifespan.

Developed 20 years ago, shear-force-transferring bentonite mats or geosynthetic clay liners have already found widespread application as replacements for, or improvements to, classic compacted clay liners around the world. The largest single market for these liners is North America, followed by Europe. Market conditions in North America led to bentonite mats employing bentonite granulate bound in needle-punched or glued textile–bentonite–composite products. In Europe, the needle-punched bentonite mat with bentonite powder as the fibre-reinforced sealing element is dominant in landfill construction. Whereas glued bentonite mats are barely able to transfer the shear force (due to the necessary water-solubility of the glue that produces the sealing effect in its swollen state), needlepunched, fibre-reinforced bentonite mats must be capable of transferring shear forces over the long term, particularly on steep embankments.

The proof of a permanent sealing effect with great system effectiveness was established through experiments in the field and in the laboratory. In the evaluation of test-field excavations and lysimeter measurements, it was proved that the shear-force-transferring, needle-punched, single-layer bentonite mats with powder-form sodium bentonite possess a selfhealing capability under typical system boundary con-

In Germany, two products (Bentofix B 4000 and Bentofix BZ 6000) were recently forwarded from the

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Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

ditions. Among landfill design experts it was errone-

ciency of the overall set-up with regard to the presence of a sealing effect.

ously supposed that the thick compacted clay liners, were able, after dehydration and desiccation cracking,

Whereas the degree of efficiency of the bentonite mat was calculated as a quotient of permeation based on the volume of drainage, i.e. the amount of water from precipitation which seeps down as far as the bentonite mat, the system efficiency, in contrast, results from the permeation based on overall precipitation, and describes not only the barrier effect of the bentonite mat, but also the evaporation arising from the recultivation layer and vegetation. It is obvious that, each summer, the efficiency of the bentonite mat is reduced through desiccation processes, but that these are also compensated for by evapotranspiration from the recultivation layer/vegetation, such that a high degree of system efficiency, approximately 98 to 99%, is maintained. Equally obvious is the level of improvement in the efficiency of the Bentofix® GCL each winter, which repeatedly reaches the level of the previous year. Since an ion exchange took place (an exchange of

to (self)-heal the polyhedral aggregate structure and to restore adequate sealing effectiveness in the long term. The measurements taken by a special lysimeter system since 1998 have provided proof of the long-term sealing effect through changing moisture conditions. To date, this system, consisting of six individual lysimeters, is still in continuous operation, involving scientists, engineers and other personnel from the University of Hanover’s department for Foundation Engineering, Soil Mechanics and Hydropower. The set-up and initial measurement results are described in detail.3 The results clearly show the differences between dry periods in the summer months and wet periods in the winter. As an example, Figure 4 shows, for one lysimeter, the corresponding degree of efficiency of a standard

efficiency [%] .

Bentofix® bentonite mat, as well as the system effi-

100

99.8

99.2

90 98.9

99.7

99.2

98.9

98.8 98.6

99.6

98.4

99.2

98.0

97.9

97.2

97.3

98.9

70 60

water flow measurements [mm]

efficiency of the GCL

98.4

95.1 93.1

81.0

78.2

75.2

74.8

69.2

99.3

97.7 96.9

97.4

90.9

99.5

98.1

76.4

efficiency of the whole system

700 619.6

600 500 390.7

377.1 390.1

400 300 259.5

290.1

275.4

5.4 2.4

1.0

316.8

254.5

9.5 3,2

3.1

42.0 4.2

295.2

264.6 229.9 189.8

183,0

6.6

5.2

372.7

324.4

228.5

224.3

34.8 0.4

388.7

300,6

200 100

424.2

6.3

9.7 3.2

6.1

6,8 6.0 1.9

351.6 288.4 189.9

11.5 2.7 14.0

18.8 5.8

jan 99 - may 99 - nov 99 - may 00 - nov 00 - may 01 - nov 01 - may 02 - nov 02 - may 03 - nov 03 - may 04 - nov 04 - may 05 - nov 05 - may 06 oct 06 apr 06 oct 05 apr 05 oct 04 apr 04 oct 03 apr 03 oct 02 apr 02 oct 01 apr 01 oct 00 apr 00 oct 99 apr 99 winter summer winter summer winter summer winter summer winter summer winter summer winter summer winter summer

rainfall

drainage

permeation

Figure 4. Lysimeter 3 – effects of summer and winter cycles on the sealing efficiency of a single-layer, standard Bentofix® bentonite mat with a 1-m recultivation layer

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Cover systems for landfills and brownfields

sodium ions against calcium ions in sodium bentonite) in the bentonite layer of the bentonite mats installed in the lysimeter two to three years after installation, the results establish that there is no reason to fear a reduction in the quality or sealing efficiency of Bentofix® or in the efficiency of the system following ion exchange in surface sealing systems of comparable design, even after many alternating dry and wet cycles.

logical analogies does not lead to results that suggest longer-term stability, or equally, the long-term efficiency of clay as a sealing layer. This has been demonstrated by findings from field studies, for example by Albright et al.1,2 Unconditional faith in the stability and effectiveness of the mineral compacted clay (standard) sealing often creates insurmountable hurdles for technically superior alternative solutions that have proven long service lives amounting to centuries, and prevents these better solutions from making a contribution to the super-ordinate goal of environmental protection. In the sense of a call for more truthfulness in dealing with landfill surface seals, the limits of material and engineering prognoses for all systems and components should be openly admitted.

These results show that geosynthetic clay liners have reached the long-term effectiveness level of HDPE geomembranes. If the quality of geosynthetic products; the quality of installation for HDPE synthetic sealing liners; and that of needle-punched geosynthetic clay sealing liners succeed in becoming appropriately established around the world, permanently effective surface sealing systems can be built anywhere in the world.

BAM-approved or GM13-tested HDPE geomembranes, produced in compliance with approval conditions and carefully installed by qualified personnel, ensure a period of utilization far beyond that forecast by all realistic engineering timeframes. Corresponding faith in the long-term effectiveness of bentonite mats that have been subjected to a German governmental (LAGA) suitability assessment, can also be anticipated.

SUMMARY AND FUTURE PROSPECTS

Because the standard sealing systems prescribed by many countries and states specify a compacted clay liner as the sealing element in administrative regulations, a paradoxical situation has developed in which these standard systems are presumed to have permanent long-term effectiveness, along with the assumption that alternative systems must first undergo extensive approval or suitability procedures to verify their ‘equivalency’ and long-term effectiveness – a lack of knowledge about the long-term effectiveness of standard mineral components has led to their extensive acceptance rather than the extensive knowledge of geosynthetics, as provided by specific proofs. In the light of current awareness about the failure of compacted clay liners in standard systems for surface seals – as a result of desiccation and forced deformation – along with the existence of approvals and suitability proofs for alternative components, it is only logical and absolutely welcome to see that geosynthetic products are finding increasing application in landfill sealing systems around the world.

Landfill engineering in the 1990s was aimed at ensuring that the landfills of our time do not become hazardous waste sites for future generations. The installation of suitability-tested, quality-monitored geosynthetics provides help around the world to achieve this lofty goal – with permanently effective surface sealing systems.

REFERENCES 1. Albright, W.H., Benson, C.H., Gee, G.W., Abichou, T., Tyler, S.W. and Rock, S.A. (2006) Field performance of three compacted clay landfill covers. Vadose Zone Journal, 5, 1157–1171 (on-line publication) 2. Albright, W.H., Benson, C.H., Gee, G.W., Abichou, T., McDonald, E.V., Tyler, S.W. and Rock, S.A. (2006) Field performance of a compacted clay landfill final cover at a humid site. Journal of Geotechnical and Geoenvironmental Engineering, November, 1393–1403 3. Blümel, W., Müller-Kirchenbauer, A., Ehrenberg, H. and von Maubeuge, K. (2003) ‘Langzeituntersuchungen zur Wasserdurchlässigkeit von Bentonitmatten in Lysimetern’. Karlsruher Deponieseminar 2002. In: Abfallwirtschaft in Forschung und Praxis, No. 125. Erich Schmidt Verlag

The standard sealing, with its singular focus on a natural mineral clay sealing as the ‘permanently’ effective sealing element is still waiting for new design and execution concepts – which are likely to incur distinctly higher overheads for verification, testing and execution. Assessment of clay minerals using minera-

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4. Gartung, E. and Schick, P. (2007) ‘Gemischtkörnige Abdichtungsschichten in Oberflächenabdichtungssystemen’. Tagungsband ‘Anforderungen an Deponie-Oberflächenabdichtungssysteme’, Status-Workshop in Höxter am 30.11/1.12.2006. Veranstalter: Arbeitskreis 6.1 ‘Geotechnik der Deponiebauwerke’ der DGGT (Deutschen Gesellschaft für Geotechnik) und Fachgebiet Abfallwirtschaft und Deponietechnik, Fachbereich Technischer Umweltschutz, Abteilung Höxter der Fachhochschule Lippe und Höxter. In: Höxteraner Berichte zu Angewandten Umweltwissenschaften, Vol. 6, June 2007 5. GDA-Empfehlung E2-13 (1997) Verformungsnachweis für mineralische Abdichtungs-schichten, GDA-Empfehlungen, 3. Auflage, 1997, pp. 135–140, Verlag Ernst & Sohn 6. Heerten, G. and Reuter, E. (2005) ‘Kritische Anmerkungen zur Genehmigungspraxis bei Deponieoberflächenabdichtungen’. 2. Symposium Umweltgeotechnik – DGGT, IFGT & CiF e.V., CiF Publication 3/2005, Freiberg, September 2005, pp. 35–52 7. Heerten, G. and Reuter, E. (2006) ‘Die mineralische Dichtungskomponente in Oberflächenabdichtungssystemen – Quo vadis?’ 22. SKZ-Fachtagung ‘Die sichere Deponie’, Würzburg, February 2006 8. Heerten, G. and Reuter, E. (2006) ‘Oberflächenabdichtungen von Deponien – Grenzen und Konsequenzen technischer Regelung’. 13. Darmstädter GeotechnikKolloquium, Darmstadt, March 2006 9. Heerten, G. and Reuter, E. (2006) ‘Erfahrungen mit der mineralischen Komponente in Oberflächenabdichtungssystemen’. Mitteilung des Instituts für Grundbau und Bodenmechanik, Technische Universität Braunschweig, Issue No. 83: Geotechnische Aspekte im Umweltschutz 2006, Fachseminar, Braunschweig, March 2006 10. Heerten, G. (2007) ‘Zur Langzeitwirksamkeit von Komponenten für Deponieoberflächenabdichtungen’, 18. Nürnberger Deponie-Seminar – Abdichtung, Stilllegung und Nachsorge von Deponien, Nürnberg, April 2007 11. Henken-Mellies, U. (2007) ‘Kombinationsabdichtungen in Oberflächenabdichtungssystemen’. Tagungsband ‘Anforderungen an Deponieoberflächenabdichtungssysteme’, Status-Workshop in Höxter am 30.11/1.12.2006. Veranstalter: Arbeitskreis 6.1 ‘Geotechnik der Deponiebauwerke’ der DGGT (Deutsche Gesellschaft für Geotechnik) und Fachgebiet Abfallwirtschaft und Deponietechnik, Fachbereich Technischer Umweltschutz, Abteilung Höxter der Fachhochschule Lippe und Höxter. In: Höxteraner Berichte zu angewandten Umweltwissenschaften, Vol. 6, June 2007 12. Institut für Grundbau, Bodenmechanik und Energiewasserbau der Universität Hannover (IGBE 2006) Versuche zur Bestimmung der ‘inneren Scherfestigkeit’ geosynthetischer Tondichtungsbahnenproben mit der Bezeichnung ‘Bentofix B 4000 mit TL’, die zuvor in besonderen Prüfgeräten einer mehrjährigen konstanten Schubbeanspruchung ausgesetzt waren, August 2006, unveröffentlichter Prüfbericht 13. Koerner, R.M. and Koerner, J.R. (1999) GRI’s First Survey of Worldwide Liner and Cover Systems. GRI Report No. 23, GSI, Folsom, PA, USA, March 1999

14. Koerner, R.M. and Hsuan, Y.G. (2003) Lifetime prediction of polymeric geomembranes used in new dam construction and dam rehabilitation. In: Proceedings Assoc. of State Dam Safety Officials Conference, Lake Harmony, Pennsylvania, 2003 15. Koerner, R.M. (2005) Designing with Geosynthetics, 5th edn. Pearson Prentice Hall, New Jersey 16. Koerner, R.M. and Koerner, J.R. (2007) GRI’s Second Worldwide Survey of Solid Waste Landfill Liner and Cover Systems. GRI Report No. 34, GSI, Folsom, PA, USA, October 2007 17. LaGatta, M.J., Boardman, B.T., Cooley, B.H. and Daniel, D.E. (1997) Geosynthetic clay liners subjected to differential settlement. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 123 (5), 402–410 18. Lehners, C. (2002) ‘Setzungsmessungen an Hausmülldeponien – Konsequenzen für den Bau von Oberflächenabdichtungen und für die Beanspruchung der Dichtungselemente’. 18. Fachtagung ‘Die sichere Deponie – Sicherung von Deponien und Altlasten mit Kunststoffen’, Würzburg 2002 19. Müller, W.W. (2003) ‘Langzeit-Scherfestigkeit von Geokunststoffen aus mehreren Komponenten’. 19. Fachtagung ‘Die sichere Deponie’, Süddeutsches Kunststoff-zentrum Würzburg, Eigenverlag, 2003 20. Müller, W.W. (2007) HDPE Geomembranes in Geotechnics. Springer-Verlag, Heidelberg 21. Ramke, H.-G., Witt, K.J., Bräcker, W. and Tiedt, M. (2007) Tagungsband ‘Anforderungen an Deponieoberflächenabdichtungssysteme’, Status workshop in Höxter am 30.11/1.12.2006. Veranstalter: Arbeitskreis 6.1 ‘Geotechnik der Deponiebauwerke’ der DGGT (Deutsche Gesellschaft für Geotechnik) und Fachgebiet Abfallwirtschaft und Deponietechnik, Fachbereich Technischer Umweltschutz, Abteilung Höxter der Fachhochschule Lippe und Höxter). In: Höxteraner Berichte zu Angewandten Umweltwissenschaften, Vol. 6, June 2007 22. Rödel, A., Kallies, B. (2002) 'Ergebnisse und Erfahrungen mit Dichtungskontrollsystemen aus der Langzeitüberwachung von Deponieoberflächenabdichtungen'. In: Abfallwirtschaft in Forschung und Praxis, Band 125: Oberflächenabdichtung von Deponien und Altlasten 2002 – Auswirkungen der AbfAblV und der DepV auf Betreiber, Behörden, Planer, Hersteller und die Bauindustrie. Herausgegeben von: Egloffstein / Burkhardt / Czurda. Erich Schmidt Verlag, Berlin 2003. 23. Witt, K.J. (2005) Plädoyer für eine angemessene Betrachtung des Langzeitaspektes bei der Planung und der Genehmigung von Oberflächenabdichtungen. In: Egloffstein et al. (eds) Abschluss und Rekultivierung von Deponien und Altlasten. Abfallwirtschaft in Forschung und Praxis, 135, pp. 81–100, Ericht Schmidt Verlag

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DOI 10.2462/09670513.908

Seasonal effect on the load in soil and subsequent transfer of arsenic to rice S.M. Imamul Huq, J.C. Joardar and A.F.M. Manzurul Hoque

Abstract The BR 29 rice variety was cultivated in potted soil (Aeric Endoaquept) for four consecutive seasons, using As-contaminated water in the dry (boro) season and fresh water in the monsoon (aman), in order to observe the effect of alternate irrigation on the As loading in the soil and on its transfer to rice. Soil arsenic content increased significantly (p = 0.003 for the first boro season and 0.013 for the second boro season) after each boro season, whereas the soil As was found to have decreased significantly (p < 0.001) at the end of both of the aman seasons. The soil As was found to be significantly reduced (p < 0.001) at the end of the fourth cropping season (boro–aman–boro–aman). At the end of the fourth cycle, the arsenic loading was found to be almost unchanged. Arsenic in rice grains was detected only when As-contaminated water was used during the boro season. Moreover, the As accumulation in rice grains was lower in the second boro season of the four cropping season cycles. Key words: arsenic, BR 29 rice, cropping season, irrigation, soil loading

INTRODUCTION

Lowland rice cultivation requires submerged and wet soils: the land is flooded by irrigation water in the dry season when boro rice is grown, and by rainwater in the monsoon when the aman rice is grown (Kyuma 2004). In Bangladesh, about 75% of the total cropped area is used for rice culture, of which approximately 78% is irrigated with groundwater in the dry season. Shallow aquifers are heavily used as the major source of irrigation water for rice cultivation, over about 80% of the total irrigated area (Ministry of Agriculture 2004). Since most of the shallow aquifers of Bangladesh are contaminated with arsenic (Burgess and Ahmed 2006), this irrigation with As-contaminated groundwater carries a risk of soil accumulation of this toxic element, Received May 2008; accepted September 2008 Authors S.M. Imamul Huq, J.C. Joardar and A.F.M. Manzurul Hoque Bangladesh-Australia Centre for Environmental Research (BACER-DU), Department of Soil, Water and Environment, University of Dhaka, Dhaka-1000, Bangladesh Corresponding author: Dr S.M. Imamul Huq, Professor and Chairman, Department of Soil, Water and Environment, University of Dhaka, Dhaka-1000, Bangladesh. Tel. 88-029661920-73/7478, 4590; 88-01819 227377 (mob), fax 88-028615583, email: imamh@bttb.net.bd; imamh@hotmail.com

357

eventually entering the food chain through plant uptake and consumption of these plants by animals (Imamul Huq and Naidu 2005). Irrigation with arsenic-contaminated groundwater is leading to elevated levels of arsenic in paddy soils (Alam and Sattar 2000), which may lead to increased concentrations of arsenic in rice (Duxbury et al. 2003; Meharg and Rahman 2003; Imamul Huq and Naidu 2005; Imamul Huq et al. 2006; Williams et al. 2006); wheat (Imamul Huq and Naidu 2005; Imamul Huq et al. 2006); vegetables (Imamul Huq and Naidu 2005; Imamul Huq et al. 2006); and other agricultural products (Abedin et al. 2002). According to Imamul Huq et al. (2006), the total As loading in irrigated soils for a boro rice requiring 1000 mm of irrigation water per season ranges from 1.36 to 5.5 kg/ha/yr. Similarly, for winter wheat that requires 150 mm of irrigation water per season, the As loading from irrigation ranges from 0.12 to 0.82 kg/ha/yr. Arsenic that enters the soil via groundwater irrigation subsequently accumulates in different parts of the rice plants (Duxbury et al. 2003; Meharg and Rahman 2003; Imamul Huq and Naidu 2005; Imamul Huq et al. 2006; Williams et al. 2006) and in different soil horizons (Imamul Huq et al. 2007a; Imamul Huq et al. 2008) to varying extents. It has been observed, how-

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

ever, that arsenic in the topsoil of rice fields increases significantly after the dry-season irrigation with Ascontaminated water (Imamul Huq et al. 2008). Arsenic thus accumulated in the topsoil would be bioavailable to the next crop of rice, even if the crop is cultivated with arsenic-free irrigation water or with rainwater (Imamul Huq et al. 2007b). A positive significant relationship between soil As and rain-fed rice-grain As (Imamul Huq et al. 2007b) observed in sites where Ascontaminated groundwater is used during the boro season, indicates the carry-over effect of irrigation-water As to rice cultivated under the alternate (As-free rainwater) irrigation system. No information is so far available on the long-term effects of As accumulation in soils and its subsequent transfer to rice grains of the same variety cultivated under the alternate irrigation system (dry-season irrigation with arsenic-contaminated groundwater followed by rice cultivation with rainwater irrigation). From this standpoint, a single variety (BR 29) of rice was grown in potted soil with alternate watering in order to obtain a clear understanding of the soil As load and of the long-term As transfer to rice (BR 29) in such circumstances.

The soil samples representing 0–15 cm depth from the surface were collected using the composite soilsampling method as suggested by the Soil Survey Staff of the United States Department of Agriculture (USDA 1951), and the samples were collected before the start of irrigation. The procedures and relevant precautions needed for proper sampling and the preservation of samples were followed, as described in Imamul Huq and Alam (2005). The collected soil samples were air dried, and the visible roots and debris were removed manually. Some of the larger and massive aggregates were broken by gentle crushing with a wooden hammer, after which the ground samples were passed through a 0.5-mm stainless-steel sieve. The sieved samples were then mixed thoroughly to make the composite sample, and were preserved for laboratory analysis. The remaining soil samples were crushed to smaller clods and passed through a 5-mm sieve. These soils were used for the pot experiment. Experimental set-up

The experiment was set up under net house conditions. Clay pots of 20-L capacity, with no drainage holes at the bottom, were used for the experiment. Each of the pots was filled with 20 kg of soil, and the pots were arranged randomly in the net house. Rice was grown with As-contaminated irrigation water in the dry (boro) season, and with As-free rainwater in the monsoon season (aman). There was only one treatment for Ascontaminated irrigation water (0.5 mgAs/L). The same variety of rice was grown for four consecutive cropping seasons (boro–aman–boro–aman). To simulate the irrigation water, normal tap water, artificially spiked with arsenic salt (sodium meta-arsenite) at the rate of 0.5 mg As/L water, was used, and the same tap water was used for irrigation for rain-fed conditions as well as for the control. Irrigation water was added every second day in the dry season, whereas water was used only when required during a relatively longer dry spell in the wet season. Care was taken not to allow the water to spill over during the wet season. However, in the second aman season (i.e. the fourth growing season) there was a spill-over on one occasion, due to incessant rainfall for two days. A total of twelve pots were used in the experiment: six as control and six for treatment. All the pots were used consecutively for each season. The background As level of the soil was 4.01 mg/kg. This

MATERIALS AND METHODS

The experiment was conducted in the net house of the Department of Soil, Water and Environment, University of Dhaka, Bangladesh. Soil sample collection and sample preparation

The floodplain of the river Ganges was selected for soil sampling. At the field selected as the sampling site, Ascontaminated groundwater has been in use for irrigation for the last five years, and the field is used for both irrigated and rain-fed rice. The site thus selected was Doyarampur village in the Gerda union (local administrative unit) of the Faridpur Sadar upazila (sub-district). The soil is a Grey Calcareous Floodplain Soil in the Ishwardi soil series (SRDI 2005) and is taxonomically referred to as an Aeric Endoaquept (Rahman 2005). The location of the sampling site is 23°33.289' N and 89°54.638' E (Figure 1). The soil is poorly drained, flooded up to 0.61–0.91 m for three to four months, and remains unsaturated for about seven to eight months in the dry season (SRDI 2005).

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Seasonal effect on the load in soil and subsequent transfer of arsenic to rice

was taken as the control. For each cropping season, the required amount of P, K, and one-third of the required N fertilizer (BARC 2005) were mixed with the soil. Of the remaining two-thirds of the N fertilizer, one-third was applied 35 days after seed sowing, and the final one-third was applied during the panicle initiation stage of the rice plants. The sources of N, P and K were urea, triple superphosphate and muriate of potash, respectively. Operations such as weeding and pest control were practised during the experimental period.

Sample collection from pots

The plants were harvested when the rice was ripening. The roots, straw and grains were collected separately. After harvest, soil samples were also collected from all the pots, and these samples were processed for laboratory analysis by following the same procedure employed earlier to prepare the field soil samples. The plant roots were washed several times with deionized distilled water, in order to remove adhering soil particles from the root surface as quickly as possible after

Upazila headquarters

Figure 1. Location map of the sampling site 359

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

sample collection. The upper parts of plants were also

Data analysis

washed. The fresh weights of the plant samples were

The experimental data were statistically analysed using the well-known statistical software Minitab 13.0.

recorded. These samples were first air-dried, and then oven-dried at 70 ± 5°C for 48 hours, and the dry weights were recorded. The dried plant samples were

RESULTS AND DISCUSSION

ground, sieved through a 0.2-mm sieve, and preserved

Arsenic in soil

for analysis.

The soil As increased significantly (p = 0.003) from its initial level after the harvest of the boro season rice (irrigated rice). However, in the control soils where Asfree tap water was used, the soil As content was reduced, and this decrease was statistically significant (p < 0.001). The arsenic build-up in soil was calculated on the basis of the initial level of As in soil and the As that accumulated in the soil after the crop is removed (Figure 2). The build-up was estimated to be 1.26 kg/ha for the boro season. After the aman rice, the soil As, both in the control and in the treated pots, decreased significantly (p < 0.001 for the treatment and p = 0.005 for the control) and the values were significantly lower than the initial values (p = 0.026 for the treatment and p < 0.001 for the control). Thereafter, the pots were used for the next boro season (under irrigated conditions). In this case again, the soil As showed a significant increase (p = 0.013) over the previous aman season values. Although this value was higher than the initial soil value, it was not significant. The estimated build-up for this season was lower than that for the first season (1.03 kg/ha). On the other hand, the As in the control soils decreased progressively, and the decrease was statisti-

Laboratory analysis

Some routine analysis of the soil samples was carried out in the laboratory, following prescribed methods as described in Imamul Huq and Alam (2005). Soil arsenic (both pre- and post-experiment) was extracted by digestion with aqua regia (HCl:HNO3, 3:1), whereas the plant arsenic was extracted by digestion with concentrated nitric acid (Portman and Riley 1964). The arsenic in the extract was estimated by hydride generation atomic absorption spectrometer (HG–AAS), with the help of potassium iodide and urea, following calibration of the equipment. Certified reference materials were used throughout the digestion, and were analysed as a part of the quality assurance/ quality control protocol. Reagent blanks and internal standards were used where appropriate, to ensure accuracy and precision in the analysis of arsenic. Each batch of ten samples was accompanied by reference standard samples, in order to ensure strict QA/QC procedures.

As spiked water

Arsenic in soil (mg/kg)

Control

5 4 3 2 1 0 Initial

ABS

AAS

ABS

AAS

Cropping seasons ABS = after boro season

AAS = after aman season

Figure 2. Changes in soil As after the harvest of four rice cropping season under the alternate irrigation system

360

Seasonal effect on the load in soil and subsequent transfer of arsenic to rice

cally significant (p = 0.024). After the fourth cropping season (second aman season), the soil As was reduced drastically and significantly (p < 0.001 for the control and p < 0.001 for the treatment). This drastic reduction could also be related to excessive rainfall during the fourth season. The reduction in soil As content from its initial value in the four cropping cycles was also significant (p < 0.001 for both the control and the treatment).

further mentioned that pot experiments tend to increase the uptake of trace elements. This phenomenon could have played an additive role in As accumulation. The As biotransformation, particularly the microbial reduction of the As content in paddy soil (Xie and Naidu 2006), and, among others, the sorption–desorption processes influenced predominantly by the clay content in soil as well as the soil pH, could govern As bioavailability to and consequent accumulation in rice plants (Horswell and Speir 2006). In the rice grown in the aman season, the As transfer from the soil to roots and shoots of the BR 29 was lower than that which occurred in the preceding boro season. This could be related to the use of As-free water. It appears that such water does not provide water-soluble As to supplement the bioavailable fraction of soil As.

Arsenic in rice

The experiment involved the cultivation of BR 29 rice in four consecutive cropping seasons on the same soil (boro–aman–boro–aman) with, alternately, As-contaminated irrigation water in the dry (boro) season and As-free rainwater in the monsoon (aman). It is clear from Table 1 that a greater amount of As accumulated in the different parts of the rice plants when they were grown with As-contaminated water. This trend of higher As accumulation is evident for both of the boro seasons. A very small fraction of As was found in rice grains throughout the four cropping seasons, particularly when it received only As-contaminated water (boro season). Arsenic in the grains of aman rice was below the detection limit (0.02 µg/kg) of the AAS (Varian Spectra 220) that was used. Moreover, a very small fraction of As was detected in rice grains of the control plants in the first boro season. This could be due to the bioavailable fraction of soil As (0.27 mg/ kg).

Arsenic could be retained in soil by various adsorption processes, which are by no means totally irreversible (McLaren et al. 2006). It is therefore likely that an increase of As in the soil, resulting from the application of As-contaminated irrigation water, could be due to the preponderance of As adsorption over the total As loss from the soil via uptake by the rice plant, biomethylation and leaching processes in the dry season. On the other hand, a decrease in As in the soil following application of As-free tap water in the dry season signifies that the desorption of As into solution could be the predominant process making the As more bioavailable to rice, as well as more liable to be volatilized to the atmosphere or leached out of the surface soil. Similarly, the decrease of As in soil after the monsoon would occur as a consequence of As desorption in the soil because As-free water was used.

In the boro season, the application of As-contaminated irrigation water provided water-soluble As which may have supplemented the inherent bioavailability of As in the soil to rice, allowing more As to be transferred from soil to rice plants in this case. It needs to be

Table 1. Mean As concentration in different parts (roots, shoots and grains) of BR 29 rice cultivated using alternate irrigation system Rice cultivation season

Type of irrigation system

Arsenic (mean ± SD) concentration (mg/kg) in BR 29 rice Roots Treatment

Control

Shoots

As load in soil (kg/ha)

Grains

Treatment

Control

Treatment

Control

Boro

As-spiked water

3.79 ± 0.23

2.48 ± 0.12

0.43 ± 0.06

0.26 ± 0.07

0.25 ± 0.04

0.02 ± 0.01

1.26

Aman

Rainwater

2.88 ± 0.13

1.98 ± 0.14

0.26 ± 0.06

0.15 ± 0.04

bdl

–

Boro

As-spiked water

3.72 ± 0.18

2.73 ± 0.11

1.63 ± 0.11

0.36 ± 0.05

0.07 ± 0.02

bdl

1.03

Aman

Rainwater

2.53 ± 0.10

1.34 ± 0.12

1.25 ± 0.09

0.25 ± 0.05

bdl

–

bdl = below detection limit (0.02 µg/kg)

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Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

Although arsenic sequestration varied in different parts of the same variety of rice in different seasons, arsenic accumulation has always been higher from Ascontaminated soils as compared to uncontaminated ones, irrespective of the season. Previous observations by the authors (Imamul Huq et al. 2006) that the total soil content has no bearing on arsenic accumulation in plants, have been further substantiated by the present study. The overall tendency for As accumulation to decrease in rice plants cultivated in both contaminated and uncontaminated soils under an alternate irrigation system rather indicates that submergence for a period of time might accentuate the bioavailability of the As and increase the subsequent mobility of the element in the soil–plant system. Yang et al. (2002) found a significant reduction in As bioavailability in soils over time. Our study suggests that application of As-free irrigation water to rice fields could substantially decrease the bioavailability of As in soil, thus reducing As uptake by rice. Moreover, our understanding of the process of slow build-up of As in irrigated fields (with As-contaminated water) needs further research. Further field studies should be carried out with more of the boro rice varieties currently cultivated in Bangladesh.

Duxbury, J.M., Mayer, A.B., Lauren, J.G. and Hassan, N. (2003) Food chain aspects of arsenic contamination in Bangladesh: effects on quality and productivity of rice. J. Environ. Sci. and Health, Part A: Toxic Hazardous Substances and Environmental Engineering, 38, 61–69 Horswell, J. and Speir, T. (2006) Arsenic phytotoxicity: effect on crop yield and crop quality. In: Managing Arsenic in the Environment: From Soil to Human Health (Naidu, R., Smith, E., Owens, G., Bhattacharya, P. and Nadebaum, P. eds), pp. 183–207. CSIRO Publishing, Melbourne, Australia Imamul Huq, S.M. and Alam, M.D. (eds) (2005) A Handbook on Analyses of Soil, Plant, and Water. BACER-DU, University of Dhaka, Bangladesh. 246 pp. Imamul Huq, S.M. and Naidu, R. (2005) Arsenic in groundwater and contamination of the food chain: Bangladesh scenario. In: Natural Arsenic in Groundwater: Occurrence, Remediation and Management (Bundschuh, J., Bhattacharya, P. and Chandrasekharam, D. eds), pp. 95–101. Balkema, Leiden, The Netherlands Imamul Huq, S.M., Joardar, J.C., Parvin, S., Correll, R. and Naidu, R. (2006) Arsenic contamination in food chain: arsenic transfer into food materials through groundwater irrigation. J. Health Popul. Nutr., 24 (3), 305–316 Imamul Huq, S.M., Manzurul Hoque, A.F.M., Biswas, A. and Joardar, J.C. (2007a) Fate of irrigation water arsenic in soil profile. In: Proceedings of International Workshop on Arsenic Sourcing and Mobilisation in Holocene Deltas (Basu, B. ed.), pp. 95–98. School of Fundamental Research, Kolkata, India

REFERENCES Abedin, M.J., Cresser, M.S., Meharg, A.A., Feldmann, J. and Cotter-Howells, J. (2002) Arsenic accumulation and metabolism in rice (Oryza sativa L.). Environ. Sci. Technol., 36, 962–968

Imamul Huq, S.M., Haque, H.A., Joardar, J.C. and Hossain, M.S.A. (2007b) Arsenic accumulation in rice grown in aman and boro seasons. Dhaka Univ. J. Biol. Sci., 16 (2), 91–97

Alam, M.B. and Sattar, M.A. (2000) Assessment of arsenic contamination in soils and waters in some areas of Bangladesh. Water Science and Technology, 42, 185–193

Imamul Huq, S.M., Manzurul Hoque, A.F.M., Joardar, J.C. and Shoaib, J.U. (2008) Arsenic movement in the profiles of some Bangladesh soils. Canadian J. Pure and Applied Sci., 2 (1), 251–259

BARC (Bangladesh Agricultural Research Council) (2005) Fertilizer Recommendation Guide – 2005 (Miah, M.M.U., Farid, A.T.M., Miah, M.A.M., Jahiruddin, M., Rahman, S.M.K., Quayyum, M.A., Sattar, M.A., Motalib, M.A., Islam, M.F., Ahsan, M. and Razia, S. eds), BARC Soils Publication No. 45. Bangladesh Agricultural Research Council, Dhaka, Bangladesh. 260 pp.

Kyuma, K. (2004) Paddy Soil Science. pp. 7–59. Kyoto University Press, Japan and Trans Pacific Press, Australia McLaren, R.G., Megharaj, M. and Naidu, R. (2006) Fate of arsenic in the soil environment. In: Managing Arsenic in the Environment: From Soil to Human Health (Naidu, R., Smith, E., Owens, G., Bhattacharya, P. and Nadebaum, P. eds), pp. 157–182. CSIRO Publishing, Melbourne, Australia

Burgess, W. and Ahmed, K.M. (2006) Arsenic in aquifers of the Bengal Basin: from sediment source to tube-wells used for domestic water supply and irrigation. In: Managing Arsenic in the Environment: From Soil to Human Health. (Naidu, R., Smith, E., Owens, G., Bhattacharya, P. and Nadebaum, P. eds), pp. 31–56. CSIRO Publishing, Melbourne, Australia

Meharg, A.A. and Rahman, M.M. (2003) Arsenic contamination of Bangladesh paddy field soils: implications for rice contribution to arsenic consumption. Environ. Sci. Technol., 37, 229–234

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Ministry of Agriculture (Sector Monitoring Unit) (2004) Handbook of Agricultural Statistics. Ministry of Agriculture, Government of Bangladesh. 81 pp.

ing, United States Department of Agriculture, Washington. 503 pp. Williams, P.N., Islam, M.R., Adomako, E.E., Raab, A., Hossain, S.A., Zhu, Y.G., Feldmann, J. and Meharg, A.A. (2006) Increase in rice grain arsenic for regions of Bangladesh irrigating paddies with elevated arsenic in ground waters. Environ. Sci. Technol., 40 (16), 4903–4908

Portman, J.E. and Riley, J.P. (1964) Determination of arsenic in seawater, marine plants and silicate and carbonate sediments. Anal. Chem. Acta, 31, 509–519 Rahman, M.R. (2005) Soils of Bangladesh. Darpon Publications, Dhaka, Bangladesh. 264 pp.

Xie, Z.M. and Naidu, R. (2006) Factors influencing bioavailability of arsenic to crops. In: Managing Arsenic in the Environment: From Soil to Human Health (Naidu, R., Smith, E., Owens, G., Bhattacharya, P. and Nadebaum, P. eds), pp. 223– 234. CSIRO Publishing, Melbourne, Australia

SRDI (Soil Resource Development Institute) (2005) Soil and Land Resource Utilization Guide for Faridpur Sadar Upazila Under Faridpur District. SRDI, Dhaka, Ministry of Agriculture, Government of the People’s Republic of Bangladesh. 91 pp.

Yang, J.K., Barnett, M.O., Jardine, P.M., Basta, N.T. and Casteel, S.W. (2002) Adsorption, sequestration and bioavailability of AsV in soils. Environ. Sci. Technol., 36, 4526–4529

USDA (1951) Soil Survey Manual. Soil Survey Staff, Bureau of Plant Industry, Soils, and Agricultural Engineer-

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Land Contamination & Reclamation, 16 (4), 2008

DOI 10.2462/09670513.901

Elemental profile of abiotic components of the East Calcutta Wetlands, a Ramsar site in India S. Chatterjee, B. Chattopadhyay and S.K. Mukhopadhyay

Abstract Beyond the eastern edge of the city of Kolkata (previously ‘Calcutta’), there is a vast wetland area. This cluster of marshlands, known as the East Calcutta Wetlands (ECW) is a Ramsar site (no. 1208) and a Wetland International Site (no. 2IN013) in India. The ECW receives composite industrial effluents, mixed with city sewage (about 600 million litres a day). Consequently, various heavy metals are transported into the area throughout the year. This composite wastewater is observed to play an important role in the ECW ecosystem, as discharges are being productively utilized in aquaculture after stabilization, and are also being used to irrigate adjoining farmland, producing around 10 915 metric tonnes of fish and nearly 370 650 kg/ha of vegetables annually. The present investigation was carried out to study the distribution of elements, namely Ca, Cr, Mn, Fe, Zn, Cu and Pb, in the various abiotic components of the wetlands, using atomic absorption spectrophotometry. For this purpose, water, bottom sediments and marginal bank soils were collected from wastewater-fed fishponds, agricultural soils and selected sites on a wastewater-carrying canal along a stretch of 40 km from the source point to the final confluence with the Kultigong river. Samples were also collected from a selected control wetland area, which was apparently uncontaminated by industrial effluent, and were compared with data collected from the study site. Variations were found in the concentration levels of various metals in abiotic components. Cr, a major constituent of tannery effluent, was found to be present in the highest concentrations, at 3.8 ± 0.31 mg L–1 and 16 495.9 ± 1480.99 mg kg–1 dw in water and bottom sediment respectively from Site 1 of the wastewater-carrying canal. The concentration of Ca was very high (279.1 ± 6.24 mg L–1) in the wastewater-fed pond-water; however, Pb was not detected in the same sample. Interestingly, a considerable decrease in the concentrations of various elements in water and sediment along the wastewater-carrying canal was recorded, indicating that the wetlands have a natural ameliorative capacity. Key words: bottom sediment, heavy metals, marginal bank soils, wastewater, wetland

and/or sediments and water in the health of aquatic ecosystems are well known. These components serve as sinks and sources of various inorganic materials; they are a component of a number of cycling processes; and they support homeostatic interrelationships with the biota (Wetzel 2001; Burton et al. 2003; Merdy et al. 2006). A variety of elements are found to occur naturally in sediments and inland aquatic environments, as a result of weathering and land drainage. The behaviour of trace elements in soils and/or sediments depends on a number of complex reactions between their ionic forms and various components of the different soil phases: solid, aqueous and gaseous, which are closely related to the soil biogeochemical systems (Kabata-Pendias and

INTRODUCTION

The significant roles of abiotic components like soil

Received April 2008; accepted August 2008 Authors S. Chatterjee,1#* B. Chattopadhyay1 and S.K. Mukhopadhyay2 1. Government College of Engineering and Leather Technology, LB, III, Salt Lake, Kolkata-700 098, India. 2. Durgapur Government College, Durgapur-713 214, West Bengal, India. (# Current address: Defence Research Laboratory (DRDO), Post Bag No. 02, Tezpur 784001, Assam, India. Tel. +91 9435738428 * Corresponding author: chats.75@gmail.com, Tel: +91 9968340424

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Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

Figure 1. The site map of the study site in the East Calcutta Wetlands, showing the selected sites (1â&#x20AC;&#x201C;4), on the wastewater-carrying canal.

Sadurski 2004). Metal ions dissolved in water generally occur as hydrated ions and as multi-molecular aggregates, due to hydrogen bonding of water molecules (Horne 1969). Moreover, bioactive elements like Ca, Fe, Mn, Cu and Zn are known to influence the migration and valence conversions of the unwanted metals like Pb (Markert et al. 2000).

tion with other metals and by metal speciation. Therefore, the distribution or partitioning of pollutants between sediments and water is a major consideration when predicting the environmental fate and transport of potentially toxic elements, including their availability to organisms. On the eastern fringe of Kolkata city, lies the largest urban wetland in India, the East Calcutta Wetlands (ECW), covering around 12 500 ha. It is a Ramsar Site, which includes 286 wastewater-fed fishponds spread over 3832.27 ha (over 30% of the total wetland area), producing nearly 10 915 metric tonnes of fish annually, and nearly 370 650 kg/ha/yr of vegetables (Chattopadhyay et al. 2002). The wetland receives raw effluent from about 538 tanneries and nearly 5500 various other small-scale industrial establishments, such as rubber and electroplating factories, pigment manufacturing units, potteries, and battery manufacturing plants, together with municipal wastewater (Chatterjee et al. 2006). Dumping of such wastes for nearly a century has resulted in the contamination of this wetland ecosys-

Anthropogenic sources are the major contributor to rises in levels of elements. Uncontrolled inputs of heavy metals in the environment are undesirable, because, once accumulated, they are hard to remove (Okoronkwo et al. 2005). Thus, over the last few decades, considerable concerns have been raised over the rise in concentrations of metallic compounds (Hunter et al. 1998). Excessive addition of heavy metals to the aquatic environment could have an adverse effect on both flora and fauna, and also on the human populations that use these organisms for food. There are a number of reports on the toxicity of metals to aquatic organisms (Bunce 1995; Treece 2000). The biological impact of the elements is complicated by their interac-

366

Elemental profile of abiotic components of the East Calcutta Wetlands, a Ramsar site in India

tem. The present investigation deals with the elemental (viz. Ca, Cr, Mn, Fe, Cu, Zn and Pb) profile in the different abiotic components, namely: water, bottom sediments and marginal bank soils of the wastewatercarrying canal, the wastewater-fed fishponds and agricultural soil from the ECW.

Water from different sites was collected in clean polythene bottles by immersing them completely in the water. Soil/sediment samples, 5–8 cm below the water surface of the wastewater-carrying canal and the ponds, were collected using a plastic shovel. The selection of the elements for analysis was carried out according to the major elements that contami-

MATERIALS AND METHODS

nate the area concerned, as per previous reports by our laboratory (Chattopadhyay et al. 1999, 2002; Chatter-

Sampling was made at four selected stations (Figure 1) in the East Calcutta Wetlands (lat. 22°27'–22°40' N; long. 88°27'–88°35' E). The first sampling station (Site 1) was located around 1 km from the Tangra tannery agglomeration (China town) of Kolkata, on a canal carrying raw composite tannery effluent. The second station (Site 2) was located at Chowbaga, a further 8 km from the source point, where the composite tannery effluent is siphoned into the storm weather flow (SWF) canal and mixed with municipal sewage through the Ballygunge drainage pumping system. The third sampling station (Site 3) was on the SWF canal near the proposed Calcutta Leather Complex at Bantala, around 15 km from the source point. The fourth station (Site 4) was on the same canal, near the Kultigong lock gate, around 40 km away from the source point. Control samples were collected from an apparently uncontaminated natural village wetland (not fed by wastewater directly from any source), nearly 75 km from the study site (Panduah, West Bengal, India).

jee et al. 2006). Detection of Ca, Cr, Mn, Fe, Cu, Zn and Pb was by atomic absorption spectrophotometer (Perkin-Elmer AAnalyst-100 with interfacing AAWinlab Software), using element-specific hollow cathode lamps in the default condition, in flame absorption mode (Chatterjee et al. 2006). Acid extraction of samples for elemental analyses was done following methods previously described elsewhere (Welz and Sperling 1999; Chatterjee et al. 2006). After filtration, water samples were acidified with concentrated nitric acid to pHs less than 2.0, and then analysed. Soil samples were dried, homogenized and sieved prior to elemental extraction from dry ash. About 1.0 ± 0.05 g of dried and ground soil was ignited in a muffle furnace at 500°C for 3 h. Acid extraction was carried out using concentrated HCl (Merck India) and concentrated HClO4 (70% pure, Merck India). Reference materials (water: SRM 1643d, estuarine sed-

Samples (water and bottom sediment) were collected from the selected study sites along the wastewater-carrying canal, from the wastewater-fed fishponds (locally called bheri) of the study area, and also from an uncontaminated fishpond as a control. Between 2003 and 2005, sampling was conducted bi-monthly throughout the year, covering all four major seasons in the lower Gangetic plains, and at three selected times of the day, namely, 08.00 hrs, 12.00 hrs and 16.00 hrs in order to ensure a good mean value. Soils were collected from the bank of the wastewater-carrying canal, over an area of approximately 3 km up- and downstream of Site 2. Similar samples were taken from the wastewater-fed fishponds and from the control wetlands. Soils from fields that had been irrigated regularly using wastewater, and had occasionally filled up with canalbottom soil sludge and solid municipal garbage, were also collected.

iments: 1646a) procured from the National Institute of Standards and Technology (NIST), were also prepared in the same way. The physico-chemical factors of the canal wastewater and of the contaminated pond water were considered. The pH, total dissolved solids (TDS) and dissolved oxygen (DO) were measured potentiometrically on site using Multiline P4 (WTW, Germany); NO3–, Cl–, total hardness, carbonate hardness, alkalinity and acidity were analysed on site calorimetrically and titrimetrically, using E. Merck (Germany) field testing Aquamerck reagent kits. Total suspended solids (TSS) were analysed gravimetrically following standard methods (Eaton et al. 1995). All gravimetric analyses, reagent and standard preparations were performed using a Mettler AE 240 monopan electronic balance.

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Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

3.1.1

RESULTS

Metals in water

The highest concentration of Ca among the four sites was recorded in samples from WW2 (260.6 ± 2.94 mg L–1), followed by WW3 (153.5 ± 9.84 mg L–1). Cr, a major constituent of tannery effluent, was recorded as being highest at WW1 (3.8 ± 0.31 mg L–1), followed by WW2 (1.4 ± 0.32 mg L–1). The highest concentration of Mn was recorded at WW2 (12.5 ± 1.13 mg L–1), while the lowest concentration was detected in samples from WW1 (1.8 ± 0.78 mg L–1). Concentrations of Fe were highest in WW1 (3.5 ± 0.23 mg L–1) and lowest in WW4 (0.82 ± 0.26 mg L–1). Interestingly, the highest concentration of Zn was recorded at WW3 (3.3 ± 0.15 mg L–1) and lowest at WW2 (1.2 ± 0.15 mg L–1). Pb was not found in WW1; however, a gradual decline in the concentration of Pb

This study presents the variations in the concentration levels of different elements, namely Ca, Cr, Mn, Fe, Cu, Zn and Pb in the wetlands, which are described below. 3.1 Metals in the wastewater-carrying canal

The concentrations of elements in samples from the four selected sites (Sites 1–4) on the wastewatercarrying canal are reported in Table 1 and Figures 2–5. For convenience, we have designated the sites (1–4), along the wastewater-carrying canal, as WW1–WW4 and BS1–BS4 for water and bottom sediment respectively.

Table 1. Metals in abiotic components (viz. water, bottom sediment, marginal bank soil and agricultural soil) collected from selected sites on the wastewater-carrying canal (WW1–4 and BS1–4 represent the water and bottom sediments of selected sites1–4), the wastewater-fed fishponds and fields in the East Calcutta Wetlands (concentration with ± SD) Metals in abiotic components from the ECW

Pond

Canal

Water (mg L–1)

WW1

55.5 ± 4.98

3.8 ± 0.31

1.8 ± 0.78

3.5 ± 0.23

0.20 ± 0.02

1.8 ± 0.21

0.00

WW2

260.6 ± 2.94

1.4 ± 0.32

12.5 ± 1.13

1.4 ± 0.27

0.28 ± 0.02

1.2 ± 0.15

0.86 ± 0.03

WW3

153.5 ± 9.84

0.14 ± 0.01

4.3 ± 0.20

1.5 ± 0.20

0.32 ± 0.01

3.3 ± 0.15

0.48 ± 0.04

WW4

94.9 ± 2.84

0.13 ± 0.02

2.5 ± 0.18

0.82 ± 0.26

0.14 ± 0.03

2.9 ± 0.38

0.17 ± 0.03

Water

279.1 ± 6.24

0.83 ± 0.09

5.7 ± 0.87

3.4 ± 0.24

0.64 ± 0.10

2.6 ± 0.21

0.00

Field

Pond

Canal

Soil (mg kg–1)

BS1

110 205.7 ± 4125.55

16 495.9 ± 1480.99

343.6 ± 16.65

20 632.7 ± 1787.63

114.8 ± 7.23

488.5 ± 32.77

53.2 ± 5.19

BS2

39 683.2 ± 1254.03

6861.3 ± 206.38

480.6 ± 28.12

25 073.7 ± 593.09

202.7 ± 5.58

608.7 ± 25.67

239.2 ± 12.43

BS3

9376.5 ± 867.79

936.9 ± 23.96

283.4 ± 16.79

21 043.1 ± 475.69

167.7 ± 11.66

431.1 ± 21.97

162.9 ± 24.14

BS4

9510.2 ± 1147.17

863.3 ± 28.51

254.6 ± 28.25

19 528.5 ± 592.09

111.1 ± 5.61

251.3 ± 14.49

91.8 ± 6.09

Marginal bank soil

33 817.7 ± 723.11

5066.3 ± 212.02

464.6 ± 15.03

22 363.1 ± 397.63

183.6 ± 14.52

573.3 ± 13.61

167.7 ± 13.78

Bottom sediment

17 205.1 ± 1157.49

747.4 ± 22.27

558.1 ± 82.15

21 566.8 ± 622.58

250.2 ± 22.89

580.5 ± 56.23

153.1 ± 18.52

Marginal bank soil

11 159.6 ± 372.65

805.1 ± 41.84

386.9 ± 26.38

19 746.3 ± 886.93

143.2 ± 17.07

435.5 ± 22.11

139.6 ± 20.34

Agricultural soil

25 419.1 ± 482.77

645.9 ± 26.72

555.5 ± 12.19

21 116.4 ± 317.86

135.6 ± 12.97

558.6 ± 31.86

98.0 ± 4.28

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Elemental profile of abiotic components of the East Calcutta Wetlands, a Ramsar site in India

5 9 8 7 4 .1

B o tto m S e d im e n t

2 2 0 2 6 .5

W a te r

8 1 0 3 .1 2 9 8 1 .0

C onc. ppm

1 0 9 6 .6 4 0 3 .4 1 4 8 .4 5 4 .6 2 0 .1 7 .4 2 .7 1 .0 0 .4 0 .1

canal, W aWastewater-carrying s te w a te r c a rry in g c a nSite a l S1ite 1

Figure 2. Profile of various metals in the water and bottom sediments of the wastewater-carrying canal at Site 1 (concentration in ppm)

59874.1

Bottom sediment

22026.5

Water

8103.1 2981.0 1096.6

Conc. ppm

403.4 148.4 54.6 20.1 7.4 2.7 1.0 0.4 0.1

Wastewater-carrying 2 Wastewater carrying canal, canal Site Site-2

Figure 3. Profile of various metals in the water and bottom sediments of the wastewater-carrying canal at Site 2 (concentration in ppm)

from WW2 (0.86 ± 0.03 mg L–1) to WW4 (0.17 ± 0.03 mg L–1) was evident from the study. 3.1.2

stituent of tannery effluent, was found to be highest at BS1 (16495.9 ± 1480.99 mg kg–1 dw). The concentration of Cr in BS3 (936.9 ± 23.96 mg kg–1 dw) was of similar magnitude to those measured at BS4 (863.3 ± 28.51 mg kg–1 dw). Concentrations of Mn at BS2 (480.6 ± 28.12 mg kg–1 dw) were observed to be highest in comparison to the other three sites. Interestingly, no significant differences between the concentrations of Fe found in the bottom sediments were observed

Metals in bottom sediment

Ca was found to be the major component for all the sites. The concentration of Ca was found to be highest in BS1 (110 205.7 ± 4125.55 mg kg–1 dw), followed by BS2 (39 683.2 ± 1254.03 mg kg–1 dw and lowest in BS4 (9510.2 ± 1147.17 mg kg–1 dw). Cr, a major con369

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

22026.5

Bottom sediment

8103.1

Water

2981.0 1096.6 403.4

Conc. ppm

148.4 54.6 20.1 7.4 2.7 1.0 0.4 0.1

Wastewater-carrying SiteSite-3 3 Wastewater carryingcanal, canal

Figure 4. Profile of various metals in the water and bottom sediments of the wastewater-carrying canal at Site 3 (concentration in ppm)

22026.5

Bottom sediment

8103.1

Water

2981.0 1096.6

Conc. ppm

403.4 148.4 54.6 20.1 7.4 2.7 1.0 0.4 0.1

Wastewater-carrying Site 4 Wastewater carryingcanal, canal Site-4

Figure 5. Profile of various metals in the water and bottom sediments of the wastewater-carrying canal at Site 4 (concentration in ppm)

(239.2 ± 12.43 mg kg–1 dw), followed by BS3 (162.9 ± 24.14 mg kg–1 dw), BS4 (91.8 ± 6.09 mg kg–1 dw) and BS1 (53.2 ± 5.19 mg kg–1dw).

across the four sites. The concentration of Fe was highest in BS2 (25 073.7 ± 593.09 mg kg–1 dw) and lowest in BS4 (19 528.5 ± 592.09 mg kg–1 dw). Concentrations of Cu and Zn in BS2 were recorded highest (Cu: 202.7 ± 5.58 mg kg–1 and Zn: 608.7 ± 25.67 mg kg–1 dw) in comparison to the other sites. Similarly, the maximum concentration of Pb was detected in BS2

3.1.3

Metals in marginal bank soil

Ca and Fe were recorded (Table 1 and Figure 7) as the major components of the marginal bank soil, with con-

370

Elemental profile of abiotic components of the East Calcutta Wetlands, a Ramsar site in India

Water

Bottom Sediment

22026.5 8103.1 2981.0 1096.6

Conc. ppm

403.4 148.4 54.6 20.1 7.4 2.7 1.0 0.4 0.1

Metals in wastewater fed pond

Figure 6. Profile of various metals in the water and bottom sediments from the wastewater-fed fishponds of the contaminated site (concentration in ppm)

centration levels of 33 817.7 ± 723.11 mg kg–1 dw and 22 363.1 ± 397.63 mg kg–1 dw, respectively. Concentrations of Cr and Pb were 5066.3 ± 212.02 mg kg–1 dw and 167.7 ± 13.78 mg kg–1 dw, respectively.

recorded as 5.7 ± 0.87 mg L–1and 2.6 ± 0.21 mg L–1 respectively. 3.2.2 Metals in bottom sediment Ca was the major component of the bottom sediment with a measured concentration of 17 205.1 ± 1157.49 mg kg–1 dw, followed by Fe 21 566.8 ± 622.58 mg kg–1 dw. Concentrations of other elements were 747.4 ± 22.27 mg kg–1 dw for Cr, 558.1 ± 82.15 mg kg–1 dw for Mn, 250.2 ± 22.89 mg kg–1 dw for Cu, 580.5 ± 56.23 mg kg–1 dw for Zn, and 153.1 ± 18.52 mg kg–1 dw for Pb.

3.2 Metals in the wastewater-fed fishponds

Table 1 and Figure 6 show the concentrations of different elements in water and bottom sediment taken from the wastewater-fed fishponds within the study site. 3.2.1

Metals in water

The concentration of Ca was very high (279.1 ± 6.24 mg L–1) in the pond water. Concentrations of Pb were below the limit of detection. The concentration of Cr was 0.83 ± 0.09 mg L–1 and Cu 0.64 ± 0.10 mg L–1 in the water. The concentrations of Mn and Zn were

3.2.3 Metals in marginal bank soil The major components of the marginal bank soil of the ponds as recorded by the study were Ca and Fe (Table 1 and Figure 7). Interestingly, concentrations of Fe

Table 2. Metals in abiotic components (viz. water, bottom sediment, marginal bank soil and agricultural soil) collected from selected sites in uncontaminated (control sites) wetland and fields (concentration with ±SD)

173.9 ± 8.73

0.00

1.7 ± 0.12

2.4 ± 0.30

0.12 ± 0.01

0.27 ± 0.02

0.00

Wetland

Bottom sediment (mg kg–1)

8387.8 ± 451.49

23.9 ± 1.36

224.7 ± 7.62

9069.3 ± 420.07

55.2 ± 7.11

84.2 ± 6.04

15.3 ± 4.71

Marginal bank soil (mg kg–1)

5727.8 ± 378.11

22.2 ± 2.96

224.7 ± 7.62

7838.1 ± 272.65

55.1 ± 7.46

73.1 ± 5.01

22.9 ± 5.59

Field

Metals in abiotic components of the uncontaminated site

Agricultural soil (mg kg–1)

7735.1 ± 46.23

17.1 ± 1.02

278.5 ± 15.04

9901.8 ± 741.17

35.6 ± 2.83

157.3 ± 8.81

19.3 ± 5.02

Water (mg L–1)

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Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

Table 3. Principal component analysis (PCA Varimax with Kaiser normalization: rotation converged in three iterations) showing the relative importance of the metals in the contaminated water and soil/sediment of the contaminated region (three components extracted for both water and soil/sediment) Water

Soil/sediment

Component

0.529

0.770

–0.029

–0.148

0.983

0.082

–0.166

0.016

0.779

0.006

0.993

–0.047

0.897

0.385

0.120

0.145

–0.078

0.974

–0.593

0.494

0.622

0.857

0.226

0.392

–0.022

0.988

–0.134

0.649

–0.271

0.549

–0.216

0.232

–0.699

0.457

0.276

0.824

0.936

–0.039

–0.109

0.949

–0.256

0.104

19 746.3 ± 886.93 mg kg–1 dw were highest, followed by Ca 11 159.6 ± 372.65 mg kg–1 dw.

highest, followed by Ca 5727.8 ± 378.11 mg kg–1 dw. Concentrations of other elements like Cr and Pb were 22.2 ± 2.96 mg kg–1 dw and 22.9 ± 5.59 mg kg–1 dw, respectively.

3.3 Metals in uncontaminated fishponds

Elements in the water of naturally occurring, apparently uncontaminated (i.e. not fed by wastewater directly from any source) fishponds are also presented for comparison (Table 2).

3.4 Metals in contaminated and uncontaminated agricultural soils

Ca and Fe were recorded as the major components of the bottom sediment, with concentration levels of 8387.8 ± 451.49 mg kg–1 dw and 9069.3 ± 420.07 mg kg–1 dw, respectively. Concentrations of other metals were 23.9 ± 1.36 mg kg–1 dw for Cr, 224.7 ± 7.62 mg kg–1 dw for Mn, 55.2 ± 7.11 mg kg–1 dw for Cu, 84.2 ± 6.04 mg kg–1 dw for Zn, and 15.3 ± 4.71 mg kg–1 dw for Pb.

The concentrations of the various elements in agricultural soils collected from both contaminated and uncontaminated study sites are presented in Tables 1 and 2. High concentrations of Ca (25 419.1 ± 482.77 mg kg–1 dw), and Fe (21 116.4 ± 317.86 mg kg–1 dw) were recorded in the agricultural soils of the study site, which was regularly irrigated using water from the wastewater-carrying canal. The concentrations of Ca and Fe in the agricultural soils of the uncontaminated site were 7735.1 ± 46.23 mg kg–1 dw and 9901.8 ± 741.17 mg kg–1 dw, respectively. Concentrations of Cr were recorded as being much higher at the contaminated site (645.9 ± 26.72 mg kg–1 dw) in comparison to the uncontaminated site (17.1 ± 1.02 mg kg–1 dw). Concentrations of Mn (555.5 ± 12.19 mg kg–1 dw) and Zn (558.6 ± 31.86 mg kg–1 dw) were found to be similar at both sites. Concentrations of other metals were 135.6 ± 12.97 mg kg–1 dw for Cu, and 98.0 ± 4.28 mg kg–1 dw for Pb at the contaminated site.

3.3.3

3.5 Statistical analysis

3.3.1

Metals in water

Cr and Pb were not found in the water on the site. However, high concentrations of Ca (173.9 ± 8.73 mg L–1) were apparent from the study. The concentration profile of the other elements was as follows: Fe (2.4 ± 0.30 mg L–1) > Mn (1.7 ± 0.12 mg L–1) > Zn (0.27 ± 0.02 mg L–1) > Cu (0.12 ± 0.01 mg L–1). 3.3.2

Metals in bottom sediment

Metals in marginal bank soil

In the marginal soil of the uncontaminated pond, Ca and Fe were also found to be the major components (Table 2). Interestingly, in the marginal soil, concentrations of Fe of 7838.1 ± 272.65 mg kg–1 dw were

The factor analyses using principal component analysis (Varimax with Kaiser normalization) were performed (Table 3) for different metals in water and bottomsediment samples from the contaminated site, and the

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Elemental profile of abiotic components of the East Calcutta Wetlands, a Ramsar site in India

Contaminated soil/sediments

Contaminated water

Table 4. Correlation matrix (r at p <0.05) between contaminated sites for water and soil and sediments collected from the wastewater-carrying canal and wastewater-fed fishponds and agricultural soil WW1

WW2

WW3

WW4

WW2

0.997

WW3

0.997

0.990

WW4

0.997

0.999

0.990

Pond water

0.998

0.997

0.999

0.997

BS1

BS2

BS3

BS4

Canal marginal soil

Pond bottom sediment

BS2

0.909

BS3

0.416

0.755

BS4

0.445

0.776

0.999

Canal marginal soil

0.897

0.999

0.774

0.795

Pond bottom sediment

0.660

0.909

0.956

0.965

0.922

Pond marginal soil

0.512

0.822

0.994

0.997

0.839

0.982

Agricultural soil

0.819

0.977

0.855

0.872

0.984

0.970

Pond marginal soil

0.908

Table 5. Physico-chemical parameters of the water from the wastewater-carrying canal and the wastewater-fed fishponds Parameters Water temperature

Units

Site 1

Site 2

Site 3

Site 4

Pond

°C

24.8 ± 2.68

25.1 ± 2.71

24.3 ± 2.59

24.4 ± 2.56

25.3 ± 2.57

7.8 ± 0.62

7.6 ± 0.62

7.3 ± 0.85

7.8 ± 0.69

8.2 ± 0.39

pH Dissolved oxygen

mg L–1

0.01 ± 0.06

0.10 ± 0.021

1.2 ± 0.54

3.4 ± 1.25

10.7 ± 1.64

Cl–

mg L–1

3759.2 ± 481.82

1621.2 ± 184.54

725.5 ± 86.30

520.0 ± 73.32

288.0 ± 14.71

NO3–

mg L–1

39.5 ± 23.30

41.1 ± 30.12

34.5 ± 25.63

60.0 ± 25.85

62.5 ± 13.69

TSS

mg L–1

1343.2 ± 298.52

344.4 ± 144.38

98.5 ± 52.89

67.3 ± 49.86

0.63 ± 0.25

TDS

mg L–1

5618.1 ± 464.79

2386.1 ± 524.85

957.6 ± 258.36

746.0 ± 123.98

428.1 ± 40.75

Alkalinity – M

mmol L–1

31.4 ± 18.88

63.6 ± 41.25

21.7 ± 19.23

10.0 ± 6.98

5.1 ± 0.63

Acidity – P

mmol L–1

1.1 ± 0.69

0.79 ± 0.41

0.7 ± 0.38

0.6 ± 0.35

0.33 ± 0.12

Total hardness

mg L–1

974.5 ± 146.45

692.5 ± 194.33

241.4 ± 65.47

196.8 ± 61.23

2.4 ± 0.56

Carbonate hardness

mg L–1

760.3 ± 116.22

528.1 ± 132.53

152.0 ± 85.70

86.2 ± 68.91

5.5 ± 1.24

the sequence for water: Pb (FL = 0.936) > Mn (FL = 0.897) > Ca (FL = 0.529), and for soil/sediment: Pb (FL = 0.949) > Fe (FL = 0.857) > Cu (FL = 0.649) > Zn (FL = 0.457). In the second component, Cu (FL = 0.988)

range of factor loading (FL) between 0.25 and 1.0 for each component was emphasized, which reveals the importance of elements in the ecosystem. The first component as per the highest factor loading, follows

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Canal region Contaminated pond region 22026.5 8103.1 2981.0

Conc. ppm

1096.6 403.4 148.4 54.6 20.1 7.4 2.7 1.0

Metals in marginal bank soils

Figure 7. Profile of various metals in the marginal bank soil of the wastewater-carrying canal and wastewater-fed fishponds (concentration in ppm)

Figure 8. Dendrogram constructed on the average metal contamination (using nearest neighbours) of the water, showing the relationships between the different sites (key: ww1 = canal wastewater Site 1; ww2 = canal wastewater Site 2; ww3 = canal wastewater Site 3; ww4 = canal wastewater Site 4; pww = pond water from the contaminated site; pwc = pond water from the uncontaminated site)

> Ca (FL = 0.770) > Fe (FL = 0.494) for water, and Cr (FL = 0.993) > Ca (FL = 0.983) for soil/sediment. For the third component, Cr (FL = 0.779) > Fe (FL = 0.622) for water, and Mn (FL = 0.974) > Zn (FL = 0.824) > Cu (FL = 0.549) > Fe (FL = 0.392) for soil/sediment. Therefore, it was interesting to note that the abundant bioactive metals were strongly interacting and/or influencing the mobility and partitioning of potentially toxic metal ions, namely Pb and Cr, available in the ambient environment. A correlation matrix (r at p < 0.05) was constructed between contaminated sites for water and

soil and sediments collected from the wastewater-carrying canal and the wastewater-fed fishponds and agricultural soils (Table 4). The water samples from all contaminated sites were highly correlated. However, a very interesting pattern of correlation between soils from different sites was noted. Positive correlation coefficients between BS1 and BS2 (r = 0.909; p < 0.05), BS2 and BS3 (r = 0.755; p < 0.05), BS3 and BS4 (r = 0.999; p < 0.05) were recorded for bottom sediments from the wastewater-carrying canal. Data from bottom sediment samples taken at site BS4 displayed

374

Elemental profile of abiotic components of the East Calcutta Wetlands, a Ramsar site in India

Figure 9. Dendrogram constructed for the average metal contamination (using nearest neighbours) of the bottom sediments, showing the relationships between the different sites (key: bs1 = canal bottom sediment Site 1; bs2 = canal bottom sediment Site 2; bs3 = canal bottom sediment Site 3; bs4 = canal bottom sediment Site 4; pbsw = pond bottom sediment from the contaminated site; pbsc = pond bottom sediment from the uncontaminated site)

the strongest association with bottom sediments sampled from the wastewater-fed fishponds (r = 0.965; p < 0.05). Interestingly, data from the samples of agricultural soils correlated well with data derived from the canal-bank soil (r = 0.984; p < 0.05).

tinct clusters were formed: (i) Sites 1 and 4 from the canal; and (ii) Site 3 from the canal and water from the uncontaminated wetland. The dendrogram (Figure 9), constructed on the bottom sediments of the wastewater-carrying canal, the wastewater-fed pond and the uncontaminated site, also revealed a distinct pattern. The bottom sediment of the wastewater-carrying canal Site 1 was furthest from the other sites, with its nearest neighbour being Site 2 on the canal.

For the water samples, three distinct clusters were identified using a dendrogram (Figure 8). Wastewater Site 2 from the canal forms a single cluster that was also the most distant from other two clusters. Two dis-

Table 6. Correlation matrix (r at p <0.05), showing the correlation between the metals and physico-chemical parameters of the water from the contaminated area Parameters

Water temperature

–0.107

–0.525

0.213

–0.923

–0.538

0.024

0.464

0.260

0.190

–0.162

0.613

0.565

–0.123

–0.678

Dissolved oxygen

0.530

–0.359

–0.100

0.383

0.845

0.355

–0.518

–

–0.526

0.952

–0.159

0.459

–0.472

–0.601

–0.123

NO3–

0.253

–0.350

–0.172

0.083

0.429

0.213

–0.518

TSS

–0.575

0.955

–0.271

0.524

–0.445

–0.528

–0.249

TDS

–0.521

0.957

–0.159

0.468

–0.464

–0.609

–0.134

Alkalinity – M

0.184

0.402

0.743

–0.206

–0.320

–0.811

0.788

Acidity – P

–0.703

0.609

–0.153

–0.075

–0.826

–0.361

0.201

Total hardness

–0.415

0.866

0.103

0.217

–0.567

–0.741

0.183

Carbonate hardness

–0.362

0.895

0.125

0.286

–0.495

–0.763

0.165

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pond were also noted. The various organic compounds and chelating agents in industrial wastewater have been found to play a significant role in the sedimentation rates of the various elements (Bryan and Langston 1992; Vallius 1999; Vulkan et al. 2002). The presence of chelating agents such as sodium formate, sodium acetate, oxalate and phenolic polycondensates in the industrial effluents, along with organic contents in this environment, may play a significant role in the differing distribution patterns of the elements in the sediments and water. Metal ion partitioning behaviour was influenced significantly by metal ion/ligand complex formations. Formation constants for a given ligand with a divalent metal ion were in the order: Ca2+ < Mn2+ < Zn2+ < Cr2+ < Fe2+ < Cu2+ < Pb2+ (Neiboer and Richardson 1980). The metal–ligand equilibrium constant was highly influenced by the series, and could be determined by this order. However, in acid–base equilibria of inorganic and organic types of ligand, pH was an important factor, as the protons competed with metal ions and, depending on the pH of the aqueous solution, displaced the metals from the binding sites and vice versa. The physico-chemical factors of the study sites (Table 5); correlation coefficient values calculated between such factors and the metal load (Table 6); and the results of the principal component analyses (Table 7), strongly suggested the influences of various physical and chemical factors in metal portioning and the role of metal–metal interactions in sequestering metal from the dissolved to the sedimentary phases. For example, Cr speciation was highly correlated with TSS (r = 0.955; p < 0.05), TDS (r = 0.957; p < 0.05), total hardness (r = 0.866; p < 0.05) and carbonate hardness (r = 0.895; p < 0.05). The toxic metal Pb was correlated with temperature (r = 0.464; p < 0.05) and total alkalinity (r = 0.788; p < 0.05). The PCA (Varimax with Kaiser normalization) on physico-chemical factors also showed interesting results (Table 7). The first components were: Cl– (FL = 0.991) > TDS (FL = 0.990) > TSS (FL = 0.989) > carbonate hardness (FL = 0.909) > total hardness (FL = 0.908). The second components were: pH (FL = 0.986) > DO (FL = 0.791) > NO3 (FL = 0.739). The major third component was total alkalinity (FL = 0.846). The effects of physico-chemical factors on metals, as reported by other authors (Campbell et al. 1997), were supported by the study. Metal speciation between dissolved and particulate phases and competi-

4 DISCUSSION

Pronounced deposition of elements in the bottom sediment from the wastewater was noted in both the canal and the fishponds. It was apparent from the study that the concentrations of all seven elements in the bottom sediment were much higher than in the overlying water. This was due to the constant sedimentation processes occurring naturally throughout the year along the wastewater-carrying canal. The SWF canal’s physical features and its flow rates influenced the various chemical interactions within the wastewater. Chattopadhyay et al. (2002) reported that the water velocity in the SWF canal varied from 0.061 to 0.333 m s–1. Such quiescent flow is likely to enhance the settling process and cause less scouring and erosion, thus ultimately leading to lower concentrations of TSS from Site 1 to Site 4 from the canal. The fishponds were also being fed daily with wastewater, and so the concentrations of the elements in the sediments were also significantly higher than in the overlying water. This was consistent with the concept that bottom sediments contain higher concentrations of metals than the overlying water (DePinto and Martin 1980). The concentrations of all the elements studied, except Cr, in the bottom sediment of Site 2, were found to be higher than those of Site 1. This was because Site 2 was at the confluence of municipal sewage with the existing industrial wastewater-carrying canal. Therefore, there were fresh inputs of several elements, which were mostly bioactive. It was also interesting to see that the concentration of Cr was found to be highest at Site 1, as the wastewater-carrying canal was primarily transporting the wastewater from tanneries and other industries. Therefore, the concentration of Cr in the environment basically occurs due to anthropogenic activities, including tanning and pigment manufacturing (Stoecker 2004). Metal concentrations in the bottom sediments were higher than those in the bank soils. Processes such as fauna–floral uptake, as well as leaching, are likely to be responsible for reducing the concentrations of metals in the bank soils (Anke 2004). However, in the bottom sediments, metal concentrations were usually higher, due to cumulative accumulations by way of metal precipitation from the wastewater, along with the settling of TSS and organic detritus. Element-specific rates of sedimentation from the water into the bottom sediments of the canal or

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Elemental profile of abiotic components of the East Calcutta Wetlands, a Ramsar site in India

tive interactions play a major role in the bio-availability of metal, which was a function of free metal concentration or activity (as a thermodynamic measure of metal reactivity) rather than of the total, dissolved metal concentration. Incorporation and adsorption of heavy metals on the surfaces of the settling particles affect the residence time, residual concentration and ultimate fate of the elements in the wastewater (Anderson and Morel 1982; Morel 1986; Zhang et al. 1997). The anthropogenic inputs of the major bioactive elements like Ca and Fe in soil/sediment/water can result in alteration of the sedimentation and complexation properties of metal–metal interactions in the system. As an example, the ubiquitous availability of Fe and its ability to adjust oxidation states, make it suited to participating in a large number of chemical reactions (Schumann and Elsenhans 2004). In the study, it was evident that the Mn concentration in the water of Site 2 at the wastewater-carrying canal was very high. It was found that at this site on the wastewater-carrying canal, the concentrations of Ca and Fe in the water and/or bottom sediment were higher as compared to other sites, which might influence the sedimentation of other elements, like Mn. It has been pointed out by other workers that Fe/Mn-rich particulates, soil redox potentials and hydrogen sulphide were the most significant abiotic factors controlling trace-element behaviour (Bartlett 1999). The statistical analyses provided an interesting result: suggesting that abundant bioactive elements strongly interacted with and/or influenced the mobility and partitioning of the other unwanted metal ions, namely Pb and Cr, available in the ambient environment.

Table 7. Principal components analysed among the physico-chemical parameters of water from the contaminated areas by the PCA (rotation method: Varimax with Kaiser normalization, a rotation converged in five iterations) Component 1

–0.457

–0.856

0.220

0.127

0.986

–0.098

Dissolved oxygen

–0.552

0.791

–0.262

Cl–

0.991

0.068

0.115

NO3–

–0.580

0.739

–0.330

TSS

0.989

0.147

0.003

TDS

0.990

0.081

0.118

Alkalinity – M

0.265

–0.463

0.846

Acidity – P

0.866

–0.497

0.044

Total hardness

0.908

–0.178

0.380

Carbonate hardness

0.909

–0.113

0.401

Water temperature

Kolkata city, along with other effluent, and was mixing these with the effluent coming from the neighbourhood of Site 1. A reduction in the concentrations of elements in the wastewater at the confluence (Site 4) with the Kultigong river in relation to Site 1 and Site 2 was noted. The average reductions in the concentration of elements were 63.6% for Ca; 96% for Cr; 80.3% for Mn; 75% for Fe; 54.8% for Cu; and 80% for Pb in the wastewater of the canal from Site 1 or Site 2 to Site 4. Significant reductions in metal concentration levels were also recorded in the bottom sediments: 91.4% for Ca; 94% for Cr; 47.7% for Mn; 22.42% for Fe; 45.9% for Cu; 53.4% for Zn; and 61.6% for Pb. ECW has attracted particular attention from environmentalists for taking the tannery waste load, both effluent and solid wastes in different forms, that were released over the last c. 100 years from three large tannery agglomerates bordering the ECW. Therefore, the scientific community was especially interested in studying the impact of waste chromium on the biota. Interestingly, the chromium build-up in the soil/sediment of the sites nearer to the tannery agglomerates (Site 1) was recorded as high as 16 560 (SD ± 1802) mg kg–1 dw, whereas the Central Pollution Control Board (CPCB), India, has set the limit for acceptable toxic concentrations in wastes at 5000 mg kg–1 dw. The high Cr concentration at Site 1 dropped to 861 (SD ± 35) mg kg–1 dw at the distant collection site near the confluence (Site 4), and was well

5 CONCLUSIONS

Gradual natural amelioration of waste metals along the course of the canal was evident from the study. The inherent value of wetlands in water treatment and the improvement of water quality has been pointed out by several workers (Kadlec and Alvord 1989; Reed 1991). The study found that a significant decrease in the metal content of both water and sediment along the wastewater-carrying canal was taking place. Most of the metals were ameliorated within the 30–32 km course of the canal. As mentioned earlier, Site 2 of the wastewatercarrying canal was receiving municipal sewage from

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within the acceptable concentration set by the CPCB for Cr. The microbial involvement in the process might be the factor that reduces the metal concentration (Patrick 1990; Naidu et al. 2002). Zhang et al. (2000) pointed out that wastewater could be remediated by wetlands, and assessed the issue. Delgado-Sanchez (1995) researching the long-term wastewater discharge into a wetland in Louisiana, and recently Day et al. (2004), have pointed out that the use of wetlands for wastewater treatment has a number of ecological and economic benefits. ECW therefore have an inherent capacity to ameliorate the metal contamination and to improve water quality, thus saving both money and energy for the region.

Bunce, N.J. (1995) Aspects of the environmental chemistry of the elements. In: Encyclopaedia of Environmental Biology, Vol. I, pp. 105–138. Academic Press Inc., N.Y. Burton Jr, G.A., Denton, D.L., Ho, K. and Ireland, D.S. (2003) Sediment toxicity testing issues and methods. In: Handbook of Ecotoxicology (Hoffman, D.J., Rattner, B.A., Burton Jr, G.A. and Cairns Jr, J. eds), pp. 111–150. Lewis Publishers, Boca Raton, FL Campbell, P.G.C., Twiss, M.R. and Wilkinson, K.J. (1997) Accumulation of natural organic matter on the surfaces of living cells: implications for the interaction of toxic solutes with aquatic biota. Can. J. Fish. Aquat. Sci., 54, 2543–2554 Chatterjee, S., Chattopadhyay, B. and Mukhopadhyay, S.K. (2006) Heavy metal distribution in tissues of cichlids (Oreochromis niloticus and O. mossambicus) collected from wastewater-fed fishponds in East Calcutta Wetlands, a Ramsar Site. Acta Ichthyologica et Piscatoria, 36 (2) 119–125

ACKNOWLEDGEMENTS

Chattopadhyay, B., Gupta, R., Chatterjee, A. and Mukhopadhyay, S.K. (1999) Characterization of tannery effluents envisaging environmental impact assessment. J. Am. Leather Chem. Assoc., 94 (9), 338–347

The authors gratefully acknowledge the cooperation and help, including a research fellowship, from the Centre Director, UGC DAE Consortium for Scientific Research, Calcutta Centre, Salt Lake City, Kolkata 700098. They also wish to thank the AICTE for granting the necessary funds for laboratory set-up (F. No. 8020/RID/TAPTEC-49/2001-2002, dated 4 February 2002). The authors also express their gratitude to the Director of Technical Education and the Director of Public Instructions, Govt. of West Bengal, India, for their cooperation and support.

Chattopadhyay, B., Chatterjee, A. and Mukhopadhyay, S.K. (2002) Bioaccumulation of metals in the East Calcutta wetland ecosystem. Aquat. Ecosys. Health Manage., 5 (2), 191–203 Day Jr, J.W., Ko, J.Y., Rybczyk, J., Sabins, D., Bean, R., Berthelot, G. et al. (2004) The use of wetlands in the Mississippi Delta for wastewater assimilation: a review. Ocean Coast. Manage., 47, 671–691 Delgado-Sanchez, P. (1995) Effects of longterm wastewater discharge into the Cypiere Perdue forested wetland at Breaux Bridge, Louisiana. Master’s Thesis, Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge

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379

Report of the NICOLE/SAGTA workshop: Sustainable remediation 3 March 2008, London, UK, compiled by Paul Bardos*

1 Introduction

Contents

Achieving sustainable development

Introduction

has been a long-term goal of

Presentations

national policies throughout

2.1

Sharing experience helps translate policy into practice

Europe. For the UK, development of

2.2

NICOLE Network on Industrially Contaminated Land in Europe 384

brownfield sites has been an important aspect.

381 382

2.3

Sustainable Remediation Forum (SURF-UK)

2.4

Sustainable remediation, regulatory and policy aspects

2.5

Sustainable remediation of contaminated sites in Switzerland 389

â&#x20AC;&#x201C; possibilities and barriers in the EU

385 387

The possibility and implications of

2.6

Regulatory approach in the UK

392

encountering contamination on

2.7

Tools for evaluating sustainability: REC and ROSA

393

such land as a result of both current

2.8

and former land use has in turn been recognized. Moreover, we have provisions in policy and guidance

Use of costâ&#x20AC;&#x201C;benefit analysis to quantify sustainability of remediation

396

2.9

An example of sustainable remediation

397

Breakout sessions

3.1

Defining sustainable remediation

that acknowledge the need to prop-

3.2

Towards implementation

399 400

erly characterize land and, when

Discussion

401

necessary, deal with contamination

Concluding remarks

403

as part of development. In the European context, similar priorities apply.

portfolio of initiatives, regulation,

process. At the same time, these

design standards and guidance that

same principles would also be rele-

Placing this in the wider context of

seek to underpin the application of

vant to other circumstances where

the goal of achieving sustainable

such principles throughout the

the undertaking of land remediation

development, there is an inevitable

development process of land prepa-

is a factor, such as work required to

need to undertake the individual

ration; infrastructure; building; and

address statutory regulations.

elements of the development proc-

ongoing management in both the

ess in ways that will individually

UK and Europe.

The SAGTA/NICOLE Workshop on

contribute to this aspiration. Indeed, there is an ever-expanding

* NICOLE Information Manager, r3 Environmental Technology Limited, www.r3environmental.com

3 March 2008 drew together curUndertaking the land-remediation

rent thinking and approaches, the

components of development with

issues of both benefits and costs, as

approaches that recognize princi-

well as the perceived gaps and

ples of sustainability therefore

uncertainties that may act as spe-

forms a significant element of the

cific challenges to achieving sus-

381

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

SAGTA SAGTA (The Soil and Groundwater Technology Association) is a non-profit-making association of organizations drawn from cross-sectoral UK land-holder companies with interests in contaminated-land management. It was initiated in 1995 with assistance from the UK’s then Department of the Environment, to act as an authoritative sounding board for industry’s views. SAGTA’s aims and objectives are to: • actively contribute to help form policy and translate it into practice; • stimulate and accelerate development of the most cost-effective technologies and methodologies; • review and share members’ experiences through case studies. SAGTA has 18 member organizations. Members must be property ‘problem’ holders, active in land management. For further information please visit SAGTA’s website: www.sagta.org.uk. Membership fees are currently £2,900 per year, and for further information please contact SAGTA’s Secretary: Douglas Laidler, Secretary SAGTA, c/o Atkins, Woodcote Grove, Ashley Road, Epsom KT18 5BW, UK. Tel. +44 (0) 1372 726140, email douglas.laidler@atkinsglobal.com

NICOLE NICOLE (Network for Contaminated Land in Europe) was set up in 1995 as a result of the CEFIC ‘SUSTECH’ programme. NICOLE was created to bring together problem holders and researchers throughout Europe who are interested in all aspects of contaminated land. It is open to public- and private-sector organizations. NICOLE was initiated as a Concerted Action within the European Commission’s Environment and Climate RTD Programme in 1996. It has been self-funding since February 1999. NICOLE’s overall objectives are to: • provide a European forum for the dissemination and exchange of knowledge and ideas about land contaminated by industrial and commercial activities; • identify research needs and promote collaborative research that will enable European industry to identify, assess and manage contaminated sites more efficiently and cost-effectively; and • collaborate with other international networks, and encompass the views of a wide range of interest groups and stakeholders. NICOLE currently has 145 members. For further information, please visit www.nicole.org. Membership fees are currently €3,500 p.a. for companies (€1,750 for SMEs), and €150 for academic institutions. Please contact: Ms Marjan Euser, Secretariat NICOLE, TNO, PO Box 342, 7300 AH Apeldoorn, The Netherlands. Tel. + 31 55 5493 927, fax +31 55 5493 231, email marjan.euser@tno.nl tainable remediation. All reports by

regulatory matters in more detail. A

sions based on points raised during

SAGTA can be found on the SAGTA

series of case studies of decision-

the meeting, and comments from a

website: www.sagta.org.uk.

support approaches and instances

number of delegates after the meet-

of sustainable remediation provided

ing.

Presentations were divided into two

examples of implementation. These

themes: defining sustainable reme-

two themes of defining and imple-

diation and how sustainable devel-

menting ‘sustainable remediation’

opment might be better

were then explored further in two

implemented in remediation. Sev-

parallel syndicate sessions in order

eral speakers from NICOLE, SAGTA

to provide conclusions for the meet-

and English Partnerships provided

ing.

scene-setting viewpoints, with

2 Presentations 2.1 Sharing experience helps translate policy into practice Paul Walker, SAGTA chairman The Soil and Groundwater Technol-

papers from the UK, Austria and

This report provides summaries of

ogy Association (SAGTA) is a non-

Switzerland exploring industry and

the papers given, along with conclu-

profit-making association of mem-

382

Clean-up & regeneration bulletin

ber organizations drawn from

review of UK research programmes

• interaction with regulators – in

cross-sectoral UK land-holder com-

in contaminated land; assessment

particular the Environment

panies with common interests in

and awareness-raising for emerg-

Agency.

contaminated-land management. It

ing methodologies/technologies;

was initiated in 1995 with assistance

links to regulators and policy mak-

To date, SAGTA has published 32

from the then Department of the

ers and other networks (e.g.

reports on workshops. It has con-

Environment, in order to act as an

NICOLE) and projects carried out

vened reports together with sum-

authoritative sounding board for

by its members. SAGTA is also a

maries on the proceedings of joint

industry’s views. The aims and

supporter of the UK demonstration

events to which SAGTA has made

objectives of SAGTA are to:

programme CL:AIRE

major contributions. All reports can

(www.claire.co.uk), providing its

be found on its website.

• actively contribute to forming policy and translating it into

chairperson since its inception, and two board members.

practice; • review and share members’

Overall, SAGTA has found that most stakeholders are willing to engage in

SAGTA has organized a wide rang-

constructive debate. However, its

experiences through case

ing series of workshops, recently

view is that such debate must be

studies;

including:

translated into actions. Contami-

• stimulate and accelerate development of most cost-

nated-land management involves • risk-based approaches in

many disciplines; however, topics

effective technologies and

contaminated-land

must be considered holistically, for

methodologies.

management;

example sustainability. Engaging

It targets areas where improvements can be made through working together, and it steers research

• planning and consents;

local authorities is difficult – while

• research into land

individuals attend, roll-out to over

contamination;

some 400 local regulators in the UK

towards knowledge gaps, as well as

• effective use of statistics;

feeding back experiences to regula-

• sustainable remediation;

tors. It is not a lobbying organization.

Planned future workshops are to

SAGTA is a network formed by

assessment.

cover mega-sites and ecological risk

by a steering group and has an

SAGTA outputs include the follow-

elected chair and deputy chair with

ing, many of which are accessible

a one-year tenure. Its interactions

via www.sagta.org.uk:

include members’ meetings and • SAGTA issues reports, papers

meetings per year, including its

and workshop position papers

annual general meeting. Member-

covering themes such as state of

ship is on a corporate basis. SAGTA

the art, exchanging perspectives,

currently has 16 member organiza-

gaps, priorities, and areas where

tions, which must be property

SAGTA can contribute;

‘problem’ holders, active in land

because regulations and regulators are more regionalized as a result of devolution. So, while SAGTA regards inclusion as very important, it is conscious that it requires more input. Engagement with national

memoranda of agreement. It is led

workshops, and it holds four formal

is problematic. This is exacerbated

regulators is very valuable to SAGTA, and, to help widen participation, SAGTA endeavours to ensure venues are convenient and adequate notice is available to ensure the resources of all parties are optimized. Future challenges identified by SAGTA include:

• projects and initiatives such as • ensuring regulation is

management, but not developers

‘Cluster’ – a project investigating

per se. Members have a primary

the prospects for small-site

interest as technology users. Activi-

remediation by using one site as

ties also include knowledge sharing

a central hub, and guidance on

facing those managing land

and dissemination; constructive

statistics;

contamination;

383

proportionate; • maintaining the profile of issues

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

• use of sustainable remediation strategies and techniques;

The NICOLE Steering Group sets

have been submitted to discussions

general policy and operational

on the Soil and Waste Framework

directions for the network. Organi-

Directives. The Groundwater Work-

zational and dissemination tasks

ing Group provided the vice-chair of

are implemented by its secretariat

the European Commission drafting

and information manager. NICOLE

group on risk assessment, and has

also includes two subgroups: one

been given the chairmanship of the

for those involved in the

for industry members (akin to

drafting group on guidance docu-

industry.

SAGTA) and one for service/tech-

ments for the Groundwater Daugh-

nology providers. Over the past year

ter Directive. The Ecological Risk

and a half, NICOLE has begun to

Assessment Working Group tracks

• encouraging technology supply to the market; • impact assessment of draft legislation and guidance; • ensuring standard competencies

These challenges will only be met by joined-up thinking from joined-up teams. The opportunity to extend networking with NICOLE is therefore welcomed.

Steering Group

2.2 NICOLE Network on Industrially Contaminated Land in Europe Johan De Fraye, NICOLE chairman

Information Manager

Industry Subgroup

The mission and ambition of

Secretariat

Service Providers Subgroup

NICOLE is to enable European industry to identify, assess and manage industrially contaminated

Figure 1. NICOLE organizational structure

land efficiently, cost-effectively and sustainably. NICOLE promotes

deliver a large amount of its techni-

the implementation of the Environ-

risk-based land management, and

cal activities via ‘working groups’

mental Liability Directive in differ-

its interests are to promote the fol-

which are open to any member of

ent countries, and its likely impacts.

lowing:

NICOLE. Currently, the following

The Brownfields Working Group is

working groups are operating in

the latest to have been initiated. Its

NICOLE:

start-up meeting was held in Bel-

• sound scientific basis; • technology development;

gium, in March 2008. Its aim is to • Groundwater;

develop an approach to the transfer

• Ecological risk assessment;

of contaminated land, allowing land

• intelligent policy;

• Monitored natural attenuation;

holders to divest land with as much

• communication;

• Soil;

confidence and certainty of a ‘clean

• sharing knowledge.

• Waste;

exit’ from liability as possible.

• best practices and evaluation tools;

• Site characterization; NICOLE’s current membership

• Brownfields.

NICOLE has a longstanding interest

includes 28 industrial companies,

in the consideration of sustainable

41 service-providing/technology-

Many of these track EU-level policy

development in contaminated land

developing companies, and 73

initiatives such as the Water Frame-

management. In March 2003,

members from universities,

work Directive and Groundwater

NICOLE organized a workshop on

research institutions, non-profit

Daughter Directive; the Soil Frame-

‘Management of Contaminated

organizations, and other networks.

work Directive; and the Waste

Land Towards a Sustainable Future:

Its organizational structure is

Framework Directive. Keynote posi-

Opportunities, Challenges and Bar-

shown in Figure 1.

tion papers produced by NICOLE

riers for the Sustainable Manage-

384

Clean-up & regeneration bulletin

ment of Contaminated Land in Europe’ in Barcelona.1 It also supported a NICOLE project on ‘Sustainability of natural attenuation of aromatics’ carried out by Bioclear, the Rotterdam Port Authority and Shell Global Solutions.2 The London workshop reflects both NICOLE’s longstanding interest in the sustainability of remediation and the initiation of a UK Sustainable Remediation Forum (SURF-

Figure 2. Key elements of sustainable development

UK), which links to a similar forum in the USA. SURF-UK is supported

In common with other countries,

in the remediation industry to

by SAGTA, CL:AIRE and English

the UK has an increasing policy

develop the concept of sustainable

Partnerships.

focus on sustainable development.

remediation decision-making. In

For example, the UK government

June 2007, CL:AIRE brought

has set an ambitious target of reduc-

together 35 key individuals from a

2.3 Sustainable Remediation Forum (SURFUK) Nicola Harries, CL:AIRE, UK

ing CO2 emissions by 60% by 2050,

variety of sectors within the brown-

compared to 1990 levels, and has

field/contaminated-land industry

launched a number of initiatives to

to pursue this concept at a meeting.

The key elements of sustainable

support these targets. Of relevance

It was agreed that participants

development are illustrated in Fig-

to the brownfield sector, is that the

would work collaboratively to

ure 2. Sustainable development

Government is looking at develop-

develop a sustainable remediation

requires a balance between eco-

ing innovation in design and con-

framework. In developing the con-

nomics, society and the environ-

struction of the built environment,

cept of a framework, provisional

ment.

and has recently launched the ‘Car-

objectives were identified:

bon Challenge’. This involves chalWith an increasing focus on the sus-

lenging house builders to build

tainability of general business prac-

zero-carbon/near-zero carbon

• Develop a common understanding within UK-SURF

tices and on accountability for

houses. This will act as a testing

of what sustainability means in

carbon emissions, the management

ground for the Government’s Code

the context of soil and

of contaminated land has also come

for Sustainable Homes, and the new

groundwater risk management/

under the spotlight. Work on con-

Planning Policy Statement on cli-

remediation, and develop a

taminated sites has traditionally

mate change, and it sees sustainable

been compartmentalized, which has

remediation of sites as a starting

not allowed the consideration of the

point.

definition. • Develop tools to quantify the net environmental value associated with soil and groundwater

environment in a holistic sense. To enhance the sustainability of out-

With regard to England, the Depart-

management/remediation

comes in the remediation of con-

ment of Communities and Local

options. Incorporate the tools

taminated land, this mindset must

Government (CLG) and Depart-

into a decision-making

change.

ment for Environment, Food and

framework for general use.

Rural Affairs (DEFRA) and English 1.Available online at http:// www.nicole.org/nicole2/news/ ann246a.pdf 2.http://www.nicole.org/projects/ displayproject.asp?project=24

• Disseminate knowledge through

Partnerships (EP), have asked

a series of position papers on

CL:AIRE to take forward an initia-

sustainability in the soil and

tive to bring together stakeholders

groundwater industry, and case

385

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

studies using the new tools in

WP4 – Review existing industry

be participating, and have also been

real examples.

tools: review existing tools and

invited to participate at Battelle 08

identify which parameters are cov-

in a special session being co-ordi-

In order to develop the framework,

ered by the different tools within the

nated by US-SURF on the same sub-

four discrete work packages (WP)

industry, and identify potential

ject.

were provisionally identified. Fig-

overlaps. Existing tools include

ure 3 sets out an overall project

those developed by: Dupont,

framework. The WPs are:

National Grid, Atkins, Golders,

Initial steps completed include:

Entec, Shell, BP, the Environment WP1 – Literature survey: under-

• set up a steering committee,

Agency, and others.

which is to include:

take a review of policy development, metrics and indicators.

– the Environment Agency CL:AIRE has recently secured fund-

– industry – Shell and National

ing through English Partnerships to

Grid Properties (SAGTA

WP2 – Review the Environment

move forward with this work. A

members)

Agency cost–benefit analysis

large amount of positive feedback

– CL:AIRE

framework: assess and test how

was received from those who

– r3 Environmental Technology

workable current guidance on cost–

attended the initial meeting was

benefit analysis (CBA) is to remedi-

received, and there have been

ation. Guidance produced for the

requests to continue running a

Environment Agency is contained

quarterly meeting to maintain

in three reports, one for soil and two

momentum. Now funding has been

for groundwater. The Agency has

secured, CL:AIRE will set up a for-

also produced a report on ‘sustaina-

mal Steering Committee to take this

ble remediation’, looking at wider

work forward along with a wider

environmental impacts. It needs to

sustainable remediation forum,

Develop a framework in order to

be separated out and the tiers

open to all. We will also continue

embed balanced decision-

unpicked to provide greater clarity,

engagement with the SURF initia-

making in the selection of the

and identify a set of generic indica-

tive in the US, which is being co-

remediation strategy to address

tors and metrics that can be applied

ordinated by Dupont.

land contamination as an

Ltd – NICOLE Working Group – link to Europe – international representative – US-SURF • create an open sustainableremediation forum; • draft a ‘vision statement’:

on a site-specific basis to pick up on

integral part of sustainable

the wider environmental impacts

UK-SURF/CL:AIRE have also been

that may have applicability to reme-

asked to co-ordinate a Special Ses-

diation. This work is currently being

sion at Consoil 08, entitled ‘Measur-

carried forward by Shell and

ing Sustainability in Remediation’

National Grid, testing the CBA guid-

in which SAGTA and NICOLE will

development.

ance on existing case studies. WP3 – Review existing tools outReview Existing Framework

side the industry: review existing tools and identify which parameters are covered by other industries’

Shell CBA Case study

sustainability assessment tools. The

Testing Framework (those viewed suitable for use) Selection of most suitable and modification as required

research will identify the different tools available; identify best-

Pilot Testing

practice examples for each type of Roll Out

tool; and detail the key reasons for successful development and implementation of the tools.

Figure 3. CL:AIRE UK-SURF project structure

386

Inside & outside industry

National Grid Case Study

Clean-up & regeneration bulletin

2.4 Sustainable remediation, regulatory and policy aspects – possibilities and barriers in the EU Dietmar Müller, EURODEMO+ and Federal Environment Agency (UBA), Austria

ber States explicitly consider sus-

pean Soil Framework Directive (to

tainable development in their

2007) do not directly specify how

contaminated-land management

sustainable development issues

policy and legislation. Taking Aus-

should be considered in contami-

tria as an example, the funding

nated-land-management decision-

guidelines for remediation projects

making. While the last version rec-

ask for a solution that is both the

ognized the importance of natural

The controlling factors for the reme-

most economic and has the best

attenuation, it did not include

ecological performance. Besides the

explicit flexibility to consider a bal-

question of whether such ‘win-win’

ance of costs and benefits, practica-

solutions are possible in reality,

bility, or secondary environmental

there are no clear criteria or defined

impacts, and this was pointed out by

approaches as to how to perform the

the Common Forum.5

diation of contaminated land are: private and public interests; site redevelopment interest; and liability management, based on the requirement to protect human health and the environment. Key considerations in selecting a remedial approach are generally: technical suitability; costs; and feasibility and practicability. The impacts of secondary environmental effects (e.g. transport, waste generation) and integrated perspectives of sustainability tend to be ignored. These wider impacts may be significant. Even technologies considered environmentally friendly, such as biological soil treatments, may end up

16 14 12 10 Treatment Transport Sum

8 6 4 2 0

0 100 200 300 400 km km km km km

with a negative environmental balance if secondary environmental impacts are taken into account. Fig-

Figure 4. Total energy consumption (TJ) for ex situ biological soil treatment of 10 000 t soil, depending on transport distances

ure 4 illustrates the impact that transport distance has on total energy consumption for a soil being biologically treated off site.

As early as the late 1990s, the European CLARINET project suggested that consideration of sustainability

assessments implied. Thus, the

Major problems in discussions on

wider environmental effects of

sustainability in land remediation

remediation options are, if

stem from the lack of a common

addressed, evaluated by loose quali-

understanding and agreed assess-

tative and non-comparable

ment approaches. The integration

approaches. Legislation on water

of ‘hard’ and ‘soft’ information

protection is strict (e.g. ground-

(such as financial costs and social

decision-making.4 Not all EU Mem-

water is generally to be protected as

impacts respectively) is a difficult

drinking water); consequently,

task. ‘Eco-efficiency’ is an assess-

3. From V. Shrenk (2005) Ökobilanzen zur Bewertung von Altlastensanierungsmaßnahmen (Environmental balancing to evaluate contaminated land remediation projects). Mitteilungshefte des Institutes für Wasserbau, University of Stuttgart – Heft 141, ISBN: 3933761-44-1. Available from www.iws.uni-stuttgart.de 4. CLARINET (2002) Review of Decision Support Tools for Contaminated Land Management, and Their Use in Europe. Available from www.clarinet.at

there is only very limited flexibility

ment technique that could be used

for considering environmental

to support decision-making that

effects or socio-economic aspects in

considers wider environmental

a broader context.

impacts. It is the ratio between a

should be a part of remediation

value (financial, ecological benefit, The European Soil Thematic Strat-

or social welfare) and environmen-

egy and the drafting of the Euro5. http://www.commonforum.eu/

387

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

tal impacts, or inversely, the ratio of

gies. The advantage is the reduction

EURODEMO considered the fol-

gained environmental value related

in wider impacts from remediation

lowing core parameters for eco-

to invested costs. Its relationship to

work. The prerequisites for sustain-

efficiency:

sustainability appraisal in an overall

ability considerations across

sense is illustrated in Figure 5.

Europe in remediation are: an

There are precedents for the use of

appropriate legislative background;

(benefits)

eco-efficiency in decision-making.

a common understanding; sound

– area of rehabilitated land

It is also a tool that has already been

technical approaches; and integra-

used in policy-making across

tion of ‘hard’ (money) and ‘soft’

Europe, for example6 by the:

information (ecological and social, socio-economic aspects and com-

• 6th Environment Action

• environmental improvements

(m2) – mass of treated contaminants (kg) and – mass or volume of treated soil/groundwater (m³);

munication).

Programme (2001), which

• environmental impact categories

suggests that consumption of

A ‘Framework for Sustainable Land

(wider impacts)

resources should not exceed the

Remediation and Management’ was

– energy consumption

carrying capacity, and a

proposed by EURODEMO, which

decoupling of resource use and

focuses on developing a simple indi-

waste generation from economic

cator-based assessment system for

growth;

the environmental dimension of

• Thematic Strategy on the

sustainability for different levels of

Sustainable Use of Natural

decision-making as shown in Figure

Resources (2005), which

6. Eco-efficiency was seen as a tech-

encompasses life-cycle thinking,

nique that could illustrate ratios

integrated to sectoral policies;

between value (financial, cost, price,

• European policy towards energy

(cumulative energy consumption: TJ) – water consumption (total water consumption: m³) – generated waste (total waste generation: kg) – global warming (indicator parameter: kg CO2).

wealth, or social welfare) and envi-

For each comparison these core

efficiency (e.g. Green Paper

ronmental impacts; that was easy to

parameters could be used to derive

2005).

control and effective; could be

assessments, such as:

applied across different levels; that Common eco-efficiency-led goals

used easily available data; and could

• Euro/m² rehabilitated land;

are: ‘decoupling’, i.e. providing the

be easily communicated to stake-

• environmental intensity

same service but with less environ-

holders.

indicators such as cumulative

mental impact, in particular ‘Factor 4’: double the service but half the impacts. One of the key objectives of EURODEMO7 and its successor initiative EURODEMO+ is to support the selection of sustainable remediation approaches, and to strengthen the competitiveness of ‘new’ technolo6. EC papers: ‘Environment 2010: Our future, our choice’ – the Sixth Environment Action Programme’; COM (2001) 31 final; ‘Thematic strategy on the sustainable use of natural resources’ COM (2005) 670 final; and ‘Green Paper on energy efficiency: doing more with less’ COM (2005b) 265 final 7. www.eurodemo.info

Figure 5. Relationship of eco-efficiency to sustainability appraisal

388

Clean-up & regeneration bulletin

• private and public sector (technology application) – decision support at the planning phase of a siteremediation project – tendering for remediation projects and – final reporting of remediation projects; • public sector (monitoring and reviewing policy) – monitoring the land remediation sector for general developments Figure 6. EURODEMO sustainability framework for soil and water remediation

(compilation, reporting and review at regional, national and European levels)

energy consumption (TJ/kg

levels could support policy, and the

mass of treated contaminant).

information could be used to estab-

– development and definition of general policy targets.

lish a new basis for discussion of The suggested core parameters

general policy targets.

could be estimated during the reme-

2.5 Sustainable remediation of contaminated sites in Switzerland Bernhard Hammer, Federal Office for the Environment (FOEN), Switzerland

diation planning phase, and should

EURODEMO suggested the devel-

be recorded during the implementa-

opment of new assessment methods

tion of a remediation. The site-

for evaluating the secondary envi-

specific estimation at the planning

ronmental impacts of land remedia-

phase would offer further under-

tion projects in a quick and easy

The traditional view of Switzerland

standing and arguments to prepare

way, such as the Project Energy

is a country of alpine mountains and

the decision on the remediation

Index proposed by Schrenk (2005).

meadows, cheese, chocolate, banks

plan. The effort required to record

EURODEMO+ also aims to develop

and watches. However, it is also a

such data during remediation would

an approach for qualitative sustain-

country with a heavily industrial-

be small, whereas the ability to opti-

ability appraisals. These tools could

ized past that has left a legacy of

mize the remediation site specifi-

be used for a range of purposes by

brownfields and waste deposits.

cally could be reasonable. With

different contaminated-land-man-

Current estimates are: 50 000 pol-

regard to soil vapour extraction,

agement actors:

luted sites; 13 000 polluted sites to

there are established benchmarks for energy intensity (energy con-

investigate; and 3000 to 4000 con• private sector (technology

taminated sites to remediate. The

sumption/kg mass of CHC), which

development and vending)

cost of managing contaminated

control the efficiency and trigger

– measuring/reporting for

land in Switzerland is estimated to

actions for optimization (e.g. energy

technology development

be €3bn, which comprises €30m for

intensity > 1000 kWh/kg CHC) and

(demonstrating innovative

registration of polluted sites;

cessation (e.g. energy intensity >

technologies)

€570m for site investigation; and

2000 kWh/kg CHC and no further

– consultants, vendors and

€2,400m for remediation. Mostly,

environmental risks). At the same

market entry of new products

these are small remediation projects

time, agreements to record and col-

and services;

– the remediation of 84% of sites is likely to cost < €600,000.

lect such data at regional or national

389

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

Switzerland distinguishes between

Prioritization of sites for remedia-

resources. Risk assessment is based

polluted sites that are operating or

tion is determined by effective envi-

on:

closed waste-disposal sites (land-

ronmental hazard and not by

fills) as well as commercial sites and

construction projects or available

accident locations at which wastes

funds. Where a site poses an imme-

dangerous is the pollutant and

were released; and contaminated

diate danger from its existing use

how much is present?

sites causing either harmful effects/

(e.g. a threat to drinking-water sup-

• release potential – how fast, how

nuisances, or give rise to a substan-

ply), remediation proceeds with no

far and in what quantities will

tial danger that such effects might

delay. Where a site poses a signifi-

pollutants be released and

occur. Such sites require remedia-

cant danger, or where concentration

tion. The Swiss policy prefers reme-

levels slightly exceed threshold lev-

diation that is effective in the long-

els, the degree of urgency is based

term and sustainable. ‘Sustainable’

on risk assessment. Remediation

means that after no more than one

does not proceed without risk

or two generations, the remediated

assessment. Sites must be evaluated

site can be safely left to posterity

on a case-by-case basis. The deter-

tion projects to be authorized. The

without any further measures. The

mining factor is not only the pollu-

goal is that projects will be success-

Swiss vision is to ‘clean-up’ the ‘sins

tion itself, but also any possible

ful and reasonably priced. Remedia-

of yesterday’ within one generation.

impacts it may have on natural

tion measures are scrutinized to

Remediation deadline 50

Remediation „containment“

D eg rada

Remediation deadline

transported? • exposure and importance of natural resources (water, soil, air), and how might pollutants impact on natural resources? The authorities require remedia-

Remediation „Decontamination“

Remediation goal

• pollutant potential – how

System break-down

Containment with natural attenuation

Remediation goal

tion /Lix ivia tion

In this scenario, the time taken for decontamination would be less than 50 years (i.e. two generations), but, if unremediated, the contamination would persist for more than 50 years.

In this scenario, the time taken for clean-up is less than the persistence of the contamination in the absence of intervention, which is itself less than 50 years. The rationale for this is that, by the time the containment fails, the contamination impacts will be below the targets, owing to natural processes. This is the only circumstance in which containment is accepted in Switzerland.

Quick degradation/lixiviation Monitoring of NA

D eg r ad a tion /Lixiv iatio n Remediation deadline

Remediation goal

In this scenario, the time taken for remediation goals to be achieved would be less than for implementing a decontamination measure.

T= few years

Figure 7. Strategic choices in remediation selection in Switzerland (C = impact on natural resources, T = time)

390

Clean-up & regeneration bulletin

Table 1. Comparison of options for the Kölliken landfill Containment

Excavation and removal

•

long-term risk

•

excavation:

•

low initial costs

•

risk removed

•

long-term costs for treatment, maintenance, restoration,

•

high initial costs

monitoring

•

no follow-up costs

long-term use-restrictions

•

re-use generally possible

•

polluter-pays principle not ascertained

•

polluter-pays principle fully applicable

•

financial risks for the public

•

financial risks for polluters, banks

•

Æ not sustainable

•

Æ sustainable

•

ensure that they are ecologically

tionate costs would otherwise

site has an area of four hectares and

sound, technically possible and

result; and the exploitation of

operated from 1978 to 1985, and is

financially bearable. The authorities

groundwater in category A

close to a drinking-water well. The

assess the proposed measures and

groundwater protection areas is

definitively establish, in consulta-

secured, or if surface waters that

tion with the affected parties, the

are associated with groundwater

remediation objectives and meas-

outside category A water protec-

ures.

tion areas fulfil the requirements of

several hundred years. Two control

the water protection legislation

strategies were compared: decon-

regarding water quality. (Article

tamination versus containment, see

15)

Table 1. Based on this comparison,

Remediation goals are to: • stop emissions at source; • remove the need for further remediation; • protect natural resources (not

site contains a large amount of persistent contaminants which pose a substantial danger over a period of

excavation and removal (decontamThe Swiss have adopted a differentiated approach to remediation decision-making. Sites of particular

ination) was seen as most sustainable.

necessarily complete removal of

concern are those: with a high per-

pollutants);

centage of persistent organic pollut-

In 2003, the authorities decreed

ants and/or heavy metals; where,

complete excavation of the landfill

elimination of danger – with no

without intervention, the degrada-

by 2012 and excavation work

cost-intensive monitoring,

tion and lixiviation of pollutants

treatment of waste-water or air

would take >>50 years; where sub-

over many generations

stantial danger would exist over a

• achieve long-term, sustainable

• promote co-operation among

long period, e.g. several hundred

started in 2008. The speaker concluded that decontamination is the only solution for economic remedia-

years; where containment systems

tion that is effective in the long

would need to be monitored and

term. The decontamination costs

Swiss regulations allow a certain

maintained for many hundreds of

for this project are estimated to be

amount of room to manoeuvre in

years; or which are dangerous and

€330m, including infrastructure

balancing environmental impacts of

present immediate risks to the envi-

work, excavation and off-site treat-

remediation, remediation costs and

ronment. Figure 7 shows three sce-

quality requirements for natural

narios that might require

ment. Containment methods would

resources: As regards rehabilita-

‘decontamination’, containment

tion for the purpose of groundwa-

and natural attenuation.

those affected

ter protection, deviation from the

have had high costs for the longterm operation over hundreds of years. Containment costs to date

objective shall be made if: by this

The management of a former haz-

have been €75m, with annual treat-

means the total environmental

ardous waste site (Kölliken landfill)

ment and monitoring costs of €3m

impact can be lessened; dispropor-

was reviewed as a case study. This

per year.

391

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

2.6 Regulatory approach in the UK Brian Bone, Environment Agency Generally speaking, ‘sustainable remediation’ is a somewhat vague term; a more precise expression is ‘remediation in the context of sustainable development’. The background to sustainable development policy in the UK is based on the

environmental, economic and social

currently an aspirational rather

criteria.

than an enforcement position. What is needed is a framework which

Another perspective for balance is

industry and regulators can use

the spectrum between local and glo-

both to decide how to find sustaina-

bal needs. For example, reducing

ble solutions, and how to determine

local carbon use and maintaining

which solutions are sustainable.

low costs may seem sustainable at a local level, but may actually be

In the UK, the Department for Envi-

exporting impacts overseas.

ronment, Food and Rural Affairs (Defra) and the Agency have pub-

Brundtland report of 1987, which defined sustainable development as: ‘Development that meets the needs of the present without compromising the ability of future generations to meet their own needs’. The Brundtland Commission also identified three ‘elements’ of sustainable development which need be in balance in order to guarantee sustainable development. The three elements, also known as the ‘three pillars of sustainable development’ are: people, planet and profit. The key elements of sustainable development are therefore environmental (planet), economic (profit) and social (people). It is this balance that is the essence of sustainable development, rather than some single parameter such as carbon use intensity or biodiversity. Figure 8 illustrates this balance. Three example decision-making criteria might be to base a remediation decision on: cheapness, cost or carbon intensity. While laudable in their own right, these criteria on their own do not necessarily identify a sustainable solution; and they are only one of many possible indicators of sustainability. A sustainable solution takes a balanced view of a range of 8. Brundtland, G.H. (1987) Our Common Future. World Commission on Environment and Development. Oxford University Press. ISBN 0-19-282080-X. http://www4.oup.co.uk/isbn/0-19282080-X

A sustainable development policy in

lished a handbook that sets out good

the UK was first published in 1990.

practice in contaminated site man-

Most recently, the government has

agement for England and Wales,

published ‘One Future – Different

called the Model Procedures. This

Paths’ which has developed five

handbook took more than a decade

themes from the Brundtland defini-

to agree and was finally published in

tion:9

2004.11 It already includes the prospect of considering sustainable

• living within environmental limits;

development in contaminatedland-management decision-

• achieving a sustainable

making.

economy; • ensuring a strong, healthy and just society;

The model procedures identify a number of overarching steps in con-

• promoting good governance;

taminated land management:

• using sound science responsibly. The final theme dictates that uncertainties must be taken into account in understanding sustainability. The Environment Agency’s aspira-

• Risk assessment – preliminary – generic quantitative – detailed quantitative; • Options appraisal

tion is that: ‘(they) encourage

– feasible options

developers to make use of sustaina-

– detailed evaluation

ble techniques for dealing with land

– remediation strategy;

contamination and find appropriate solutions for treating and reusing contaminated soils’.10 This is 9. Department for Environment, Food and Rural Affairs – Defra (2005) One Future – Different Paths, The UK’s Shared Framework For Sustainable Development. Product code PB10591, Defra Publications, Admail 6000, London SW1A 2XX. http:// www.sustainable-development.gov.uk/ publications/pdf/SD%20Framework.pdf 10. Barbara Young, Chief Executive, Environment Agency, in The Environmental Industries Commission Land Remediation Yearbook 2007, http://www.eic-yearbook.co.uk/

392

• Risk management – implementation plan – design, implementation, verification – long-term monitoring and maintenance. 11. Defra and the Environment Agency (2004) Model Procedures for the Management of Land Contamination: Contaminated Land Report, 11. ISBN 1844322955. Environment Agency, Bristol www.environmentagency.gov.uk/subjects/landquality/ 113813/881475/?lang=e

Clean-up & regeneration bulletin

Decision-making for sustainable

and may include the following

Two sustainability considerations

development begins at the options

steps: from their identification and

can be identified for ‘sustainable

appraisal stage. The speaker’s view

comparison for different strategy

remediation’:

is that the focus of attention for sus-

options, to perhaps their monetiza-

tainability in this sequence should

tion in a cost–benefit appraisal, if

be sustainable risk management

this is seen as necessary. There

and not remediation.

should also be a mechanism for feeding back the outcome for the

Scoring systems and multi-criteria analysis have begun to be used in options appraisal under the Model Procedures, as illustrated in Figure 9. However, it is very difficult to relate such analysis tables back to the original evidence base. A range of techniques may be used in sustainability appraisals, such as multicriteria analysis, life-cycle assessment, cost–benefit analysis and various assessments for added or wider environmental value. However, the weaknesses of all of these

site to the sustainability assessment: i.e. how accurate was the sustainability assessment? There need to be pilots and case studies to develop this framework, and tools for supporting rather than submerging decision-making. As a final point, important questions are: who should carry out a sustainability appraisal, and who is it being car-

understood by interested parties. They can all potentially serve as a ‘black box’ that takes rather than supports the decision-making task.

remediation objectives, which might take into account: impact of future developments; impact of climate change; reducing future liabilities by setting the right requirements/constraints with respect to unacceptable risks; suitability for (future) land use; or plume behaviour (e.g. a stable end-situation with limited need for after-care); and • sustainability of the remediation

ried out for? A debate between

technology, which might take

experts will inevitably skew sustain-

into account: the impact of the

ability discussions to the areas in

implementation of the

which they feel most comfortable.

remediation technique itself, and reducing the impact of the

are: their transparency; their accessibility; and how easily they can be

• the sustainability of the

2.7 Tools for evaluating sustainability: REC and ROSA Laurent Bakker, TAUW, NL

technique on the environment by having the right expectations for the techniques and activities regarding the target concentrations, time frames or

The sustainable remediation debate

mass removal.

is an emerging one. A 2004 survey The ideal approach to considering

carried out in the UK collected

sustainable development in con-

responses from 60 remediation

taminated-land-management deci-

practioners. It found that ‘com-

sion-making is that it is a tiered

monly, the effects of contamination

approach using a range of tools:

on these areas both immediately

from generic approaches that can

and in the long term are taken into

involve a range of stakeholders to

account, but those of actually per-

more quantitative approaches. The

forming the remediation (transpor-

consideration should be the overall

tation, waste, etc.) are often not and

remediation strategy for the man-

so progress towards a truly sustain-

agement of a particular site, rather

able solution is hindered’. It further

than generic rules of thumb that

found that ‘professional judgement

compare particular technologies,

is exercised most commonly’ as the

and this consideration may need to

sustainability assessment approach,

be integrated with considerations of

and that more sophisticated meth-

wider activities for the site. The sus-

ods are not as widely used, meaning

tainability assessment is likely to be

that some sustainability aspects

based on key indicators or metrics,

might be being neglected.12

393

The impact of climate change in the Netherlands, for example, may have a noticeable impact on the sustainability of remediation objectives. Climate change in the Netherlands is expected to lead to higher temperatures and heavier and more frequent rainfall. Both of these consequences seem likely to have an impact on natural soil processes and thus an impact on pollutant behaviour, for example: 12. SUBR:IM bulletin SUB 02 ‘Uncovering the True Impacts of Remediation’, March 2007. http:// www.claire.co.uk/ index.php?option=com_docman&task= cat_view&gid=19&Itemid=25 (Free to download, but requires registration/login.)

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

• increased leaching/erosion (> 25%) Æ increase in pollutant

Decision based on local community involvement

mobility; • increased wetting/drying fluctuations Æ increase in pollutant mobility/damage to soil capping measures; • changes in redox conditions Æ

Decision based on cheapness

increase in pollutant mobility; • enhanced biodegradation Æ decrease in pollutant mobility affecting mineral capping.

Decision based on carbon intensity

Figure 8. Illustration of sustainable development considerations (source: Wikipedia). A single criterion will not necessarily provide a balanced sustainable approach

The sustainability of remediation is directly linked to considerations of soil functionality and threats to soil. The EU Soil Thematic Strategy13 identified a number of threats to soil resources in Europe: contamination; sealing; erosion; organic matter decline; salinization; erosion and landslides. Soil functionality provides another perspective for evaluation of the holistic approach to the environmental benefits of soil remediation. An example is the case of oil contamination in soil. At low levels, soil contamination with mineral oil is a sort of organic-matter fixation in the soil. If remediation is

Figure 9. Example model procedure-based scoring

required, how much energy is consumed and CO2 produced to convert this oil into CO2, and so what is the

Dutch national soil protection legis-

worked through in order to arrive at

balance between risk reduction and

lation.14 ROSA includes both a sim-

a point that offers (also for other

environmental benefits?

plification of the existing

stakeholders) an overview of the

assessment process within the

process and the choices that have

ROSA is a set of decision-making

Dutch legislation and tools to arrive

been made. The document gives

guidelines for dealing with com-

at a preferred remediation strategy

guidelines for an agreement con-

mon soil and groundwater prob-

in a way that is as objective as possi-

cerning flexible remediation objec-

lems. This approach was developed

ble. However, it cannot be regarded

tives, and for the organization and

for the situation in the Netherlands,

as a cookbook with clear-cut solu-

warranty of the realization of the

and is based on the latest develop-

tions for problems. The guidelines

remediation. An important aspect

ments in and interpretations of

contain the elements and phases of

of ROSA is the involvement of

a process, and each needs to be

stakeholders in order to identify

13. European Commission (2006) Thematic Strategy for Soil Protection. Communication from the Commission, Brussels, 22.9.2006. COM(2006)231 final. http://ec.europa.eu/environment/ soil/pdf/com_2006_0231_en.pdf

14. Summary in English: http:// www.nicole.org/news/downloads/ ROSA%20English%20Summarylmb%20 v2.pdf

394

their interests and gain their commitment to the process with a view to also addressing (future) develop-

Clean-up & regeneration bulletin

Table 2. The ROSA tiered approach Step

Results

Preliminary meetings with stakeholders (policy and sounding groups)

Inventory of interests, wishes and requirements of stakeholders, and the objectives of the remediation List of requirements and expectations; criteria to consider/weighing the different scenarios Mass reduction â&#x20AC;&#x201C; reduction of exposure

Scenario development (often a combination of feasible techniques)

Elaboration of possible remediation scenarios

Risks, environmental merits and costs (REC)

Uniform and transparent overview of REC for each scenario

Preferential scenario

Stepwise and transparent deduction of scenarios, resulting in one accepted scenario

Remediation plan

Agreement on monitoring, milestones and aftercare

F/G. Remediation, monitoring, evaluation and aftercare

Remediation evaluation, registration and aftercare programme

ments and finding realistic solu-

management, wider â&#x20AC;&#x2DC;environmen-

mization of environmental quality,

tions without overestimation of the

tal meritâ&#x20AC;&#x2122; and costs. This can be used

with minimum use of scarce

potentials of technologies. It is an

in remedial option appraisal to

resources.

iterative approach to manage uncer-

compare clean-up scenarios on the

tainties. Table 2 shows the tiered

basis of a full range of environmen-

approach in ROSA. Sustainability is

tal and financial costs and benefits.

considered once a series of risk-

The aims of the REC system are to:

management options have been

reduce complexity to manageable

determined. The REC tool is recom-

systems and other targets. REC con-

proportions; raise the effectiveness

mended for this assessment.

siders costs as the total costs of

of the decision-making process;

remediation practice, including:

facilitate communication and inter-

preparation; operation; and main-

The REC system (risks, environ-

pretation; and improve the strategic

tenance and monitoring, at all

mental merits and costs), used in

design of clean-up. The sustainabil-

stages of the operation, i.e. costs

the Netherlands, is designed to be a

ity aspects of the REC system are

and risk reduction are considered,

systematic quantitative remediation

contained in its environmental

with a fairly narrow focus on the

appraisal tool that considers risk

merit concept, which seeks a maxi-

basis of reasonably quantifiable

REC considers risk reduction to be the degree to which a remedial action reduces risks to humans, eco-

M1 soil quality

M3 loss of soil

-15

theoretic maximum

M4 loss of groundwater M5 use of energy M6 air emissions

in situ

M7 surface water emissions M8 waste creation M9 use of space

reference

-10

control

-5

ho in tsp -s o itu t +

excavation + pump + treat

contribution to environmental merit

M2 groundwater quality

Figure 10. Environmental merit components (example comparison)

395

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

100%

1000 500 0

Theoretic maximum MF-reference

it u

-6

1500

-s

Exposure to other objects

-4

2000

Exposure to ecosystems

-2

2500

nt ro l

Exposure to humans

3000

tu -s i in

nt ro l co

e pu xc m av a p a n t io n d tre + at

3500

e pu xca m va p ti o an n d + tre at

10%

Net Cash Value k€]

20%

4000

it u

30%

4500

MF-referentie MF-referentie

in -s

40%

Theoretisch maximum

ro l

50%

60%

70%

Environmental merit index

80%

e pu xc m ava p a n t i on d tre + at

Risk reduction [-]

90%

Figure 11. Example of REC system output

parameters. Environmental merit is

energy is being used for heating

defined as the balance between

to enhance processes such as

materials) for solidification/

environmental benefits and costs.

biodegradation, dissolution,

stabilization of soil to create new

LCA principles are used to deter-

diffusion and evaporation.

aggregates for use in road

mine environmental merit. Remediation with good ‘environmental merit’ is where limited use of natural resources and limited pollution achieves a good environmental output. The components of the environmental merit index are illustrated in Figure 10. A sample output from the REC system is shown in Figure 11.

• Phytoremediation offers a range of potential remedial solutions, for example in the management of organics dissolved in groundwater, either by using evapotranspiration as a ‘pump’ to remove contaminated groundwater from soil, or by using root-zone enhancement of microbial activity to accelerate biodegradation, or both.

• There is increasing interest in ‘extensive’ technologies, i.e.

• Bioremediation and biological

technologies that use fewer

soil treatment are seen as

resources, often trading time for

remediation approaches with a

resource intensity.

low carbon-intensity that can

• Wind energy is being used to support soil venting, both infiltration of air (high pressure) and extraction (low pressure), with aeration by wind. Windmills are also being used to support

degrade some contaminants and

• The reuse of secondary (recycled

construction. Soil remediation is a long and expensive business. The need for sustainability encompasses both sustainable remediation objectives to minimize the impact of future changes (such as climate change); and sustainable technical solutions to minimize environmental impacts from remediation itself. This is a component of a more overarching need: sustainable soil quality management. This forms part of Europe-wide discussions on soil quality and functionality, and on the linkage of these with water quality.

immobilize others. For ex situ processes they can create soil for reuse, and for in situ processes they can avoid waste generation. • An intriguing possibility is to

2.8 Use of cost–benefit analysis to quantify sustainability of remediation Stuart Arch, Worley Parsons Komex, UK

landfill gas extraction, for

combine water infiltration with

The speaker suggested that eco-

example at Volgermeerpolder,

extraction into the subsurface,

nomic remediation strategies are

which is a 100-ha landfill in a

both for seasonal heat

almost by definition sustainable at

rural area. The energy surplus

management in buildings and

one level, as they pay for them-

(wind and landfill gas) is

land remediation (an approach

selves. To bring wider sustainability

exported to the Dutch grid. Solar

discussed in Section 2.9).

considerations into corporate deci-

396

Clean-up & regeneration bulletin

sion-making, they need to be put in

corporate responsibility; and liabil-

• the need to identify clear risk-

terms of ‘money’, because that is

ity management. Examples of exter-

management goals before

what fundamentally drives busi-

nalities include: groundwater

selecting a technology;

ness decision-making. The Brundt-

resources; ecological resources;

land Commission, in 1987, defined sustainable development as development that ‘... meets the needs of the present generation without compromising the ability of future

human health protection; property blight, greenhouse gas emissions; transportation impact; option value;15 and bequest value.16

generations to meet their own

• that external costs are explicitly accounted for; • that all stakeholders’ concerns are considered on an equal basis. Cost–benefit analysis helps determine the appropriate level of

needs’. This could be translated in

Guidance on the use of cost–benefit

expenditure for a given site. How-

terms of remediation to: a ‘strategy

analysis was produced by the Envi-

ever, economic analysis is a ‘double-

ronment Agency in 1999,17 and this

edged sword’: it can justify lower or

has been applied subsequently by

higher expenditure, depending on

to repair damage caused by contamination of land or water that balances the interests of the problem holder, the environment and soci-

Worley Parsons Komex as an

ety, now and into the future’. This is

options-appraisal tool that uses

the concept behind cost–benefit

high-level economic evaluations to

analysis.

compare a range of remedial approaches, monetizing risk/dam-

the benefits produced. 2.9 An example of sustainable remediation Hans Slenders, ARCADIS, NL Philips started its activities at its

Cost–benefit analysis attempts to

age averted to identify which option

value in monetary terms two sets of

gives the greatest increase in human

costs and benefits: those that are

welfare, as measured by ‘present

‘internal’, i.e. directly related to the

value’. Options appraisal follows

over. At the peak, more than 10 000

project being carried out, and those

characterization of the nature and

people worked at this site.

that are external, i.e. wider costs or

extent of contamination and the

Redevelopment began in 2005. His-

technical risks that it poses (e.g. to

toric buildings will have new func-

human health, controlled waters,

tions, and new buildings and houses

benefits affecting the environment or society as a whole. The difference between costs and benefits is its ‘net benefit’. Usually, this is expressed in terms of ‘net present value’ (NPV),

resources, environment and property).

former Strijp site in the city centre of Eindhoven in 1915, and within 15 years its 27-ha site was fully built

will be erected to create a mixture of living, leisure and work space. The site planning includes ambitious

which is the conversion of current

sustainability concepts, including

and future values into an equivalent

Key considerations in using cost–

an integrated approach to ground-

value ‘today’. Predictive cost–

benefit analysis in remedial option

water remediation with groundwa-

appraisal are:

ter energy, due to become

benefit analysis can therefore be used as an appraisal tool to compare different remediation options under consideration to see which ones will deliver the greatest present value (PV), as illustrated in Figure 12. Examples of private costs include: management costs; investigation and remediation; consultancy; and loss of production. Examples of private benefits include: property value; avoidance of prosecution;

operational in autumn 2008. This 15. Where an individual derives benefit from ensuring that the resource will be available for his or her own use in the future. 16. Associated with the knowledge that the resource will be passed on – in suitable quantity and quality – to descendants and other members of future generations 17. Cost–benefit analysis for remediation of land contamination, R&D Project P5-015, Report TR P316 prepared by Risk & Policy Analysts Limited and WS Atkins http:// publications.environmentagency.gov.uk/epages/ eapublications.storefront/ 47ff705700ea1d16273fc0a802960677/ Product/View/STR&2DP316&2DE&2DE

397

was the first time in the Netherlands that these two concepts had been combined. Sustainable energy can be obtained from groundwater by pumping large flows, with large reductions in carbon intensity. For this site, models indicate a reduction of potentially 3000 tonnes of CO2 per head for heating and cooling, compared

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

PV costs

PV external costs

PV internal benefits

PV external benefits

PV costs & benefits

Option 1

Option 2

Option 3

Option 4

Figure 12. Conceptual comparison of four remediation options on the basis of present value (PV)

with traditional heating. While the

zone to a warm zone. With such an

municipality, while the

use of electricity would increase

approach, contaminants would also

groundwater permit is the

from 2.4 to 4.7 million kWh per

have been moved and spread. A

responsibility of the Province of

year, resulting from the use of heat

remediation system is primarily

Noord-Brabant.

pumps, the use of natural gas across

designed to contain and reduce the

the 27-ha site is projected to be

extent of contamination. The

involved in the project, for

reduced from 2.8 million m3 to less

approach taken to resolve these par-

example: the developer; the

than 600 000 m3. This results in a

adoxes and create a synergy was to

energy company; consultants;

projected reduction in energy costs

use large groundwater flows both

contractors; and authorities.

of 30–40%.

for hydraulic containment of con-

• In parallel with the groundwater

taminants and heat transfer.

• A large number of parties were

system design and realization, planning of the redevelopment of

In the winter, heat can be extracted with a heat-pump; in the summer,

As the first to involve the drafting

the site still goes on. These plans

heat can be deposited to provide a

and engineering of such a ground-

change, and evolving decisions

cooling effect. The combination of

water system, the project faced sev-

about existing infrastructure

heat-pumping and remediation cre-

eral challenges, for example:

(buildings, sewers, cables, etc.) have to be anticipated or taken

ates a number of potential design

into account.

paradoxes. The aim of a groundwa-

• The requirements for durability

ter energy system is to maximize the

and continuous groundwater

energy-transfer capacity, which

pumping for the heat system

wells is dominated by the energy

requires large groundwater flows.

required the avoidance of well-

demand in the buildings. On the

This is the first paradox in connec-

clogging, and hence the

other hand, these flows must be

tion with the remediation of

avoidance of stimulating

used to contain contaminated

groundwater. Normally, the reme-

biological activity or transfer of

groundwater, and to manipulate

diation of contaminated groundwa-

soluble ions, such as iron, around

the groundwater flow field. The

ter is designed with minimal flows

the well, both of which can lead

adjustment of these two

to well-clogging.

demands (energy and

to reduce cost. The second paradox lies in the containment of ground-

• Permitting and regulation fell

• The total flow in the extraction

containment) is essential and

water. Conventionally, in the heat–

under two different jurisdictions:

complex. The design of the

cold–storage (HCS) approach,

the remediation permit falls

groundwater system: the

groundwater is pumped from a cold

under the jurisdiction of the

coupling of wells; the

398

Clean-up & regeneration bulletin

management of pumps and

Natural degradation at the site is

Restoration Trust, UK, and

sensors; as well as the in-house

limited by the rate of the mixing of

Ruth Chippendale, Shell, UK

installations, etc., had to be well

bacteria, nutrients and contami-

tuned to provide a coherent

nants. The large volumes of water

The ‘definitions’ subgroup found its

design.

circulation greatly increase mixing

task to be a difficult one. Different

to create a ‘biowashing machine’. In

stakeholder groups, and different

ARCADIS took up this design chal-

cases where natural conditions are

lenge18 and found the first part of

insufficient, or if there is a lack of

the answer by changing the basic

nutrients, the set-up offers the

concept for the groundwater sys-

opportunity to add the necessary

tem. Instead of using cold and warm

substances to the in situ treatment

strategic decision-making in con-

zones in the subsurface, it was

zone created, taking into account

taminated-land management fol-

decided to use a recirculation sys-

constraints imposed by the need to

lows land-use contexts locally,

tem. This system uses a constant

avoid well-fouling).

regionally and nationally. The syn-

flow direction and extracts heat or Process design was modelled to

constant temperature at the Eind-

determine how far the groundwater

hoven site of 12–13°C).

system could achieve containment with a neutral water balance (water

mainly involved chlorinated solvents in the saturated zone (cisdichloroethylene and vinyl chloride) from 30 to 60 m below the ground surface. These contaminants had started to move after the groundwater extraction (that had taken place while the site was active) had stopped.

spectives on what constituted sustainable remediation. In addition,

dicate group quite liked the UK Sus-

cold from groundwater (which has a

Contamination problems at the site

individuals, had very different per-

tainable Remediation Forum19 (SURF-UK) definition, and adapted it to provide an interim position for

out = water in); the development of

NICOLE and SAGTA for a descrip-

soil and groundwater temperatures;

tion of sustainable remediation: a

and the environmental impacts of

‘framework in order to embed bal-

the system for the groundwater per-

anced decision making in the selec-

mit. Likely containment was estimated to lie between 90 and 100%. In a strong flow field it is possible that injected heat in the summer reaches the (cool) extraction wells

tion of the strategy to address land (and/or water contamination) as an integral part of sustainable land use’.

while cold is still needed. Modelling found that heat or cold travel much more slowly than groundwater.

There was also debate as to whether the concept of sustainable remedia-

By using a circulation system for

After a modelled period of 20 years,

energy extraction, an effective

it was found that neither heat nor

tion might be better approached ‘as

approach to containment is possi-

cold would reach further than 30%

remediation in a sustainability con-

ble, an approach that also enables

of the distance between infiltration

text’. The revised concept encom-

the stimulation of natural degrad-

and extraction.

passes remediation and how this

ation. In practice, the recirculation system consists of a smartly designed system of extraction and infiltration wells, as illustrated in Figure 13, which shows how the cluster of infiltration wells is surrounded by extraction wells, which capture the contaminated groundwater. 18. Feasibility testing and implementation is being carried out by Volker-Wessels.

impacts sustainable development at

3 Breakout sessions

different levels. The former concept appears to be limited to considering

Two parallel syndicate sessions took place, one focused on defining sustainable remediation and the other on the implementation of sustainability in remediation.

whether the remedial exercise alone is carried out in a sustainable way, for example, by considering emissions during transport and excavation, etc.

3.1 Defining sustainable remediation Euan Hall, Land

399

19. SURF-UK is co-ordinated by CLAIRE, www.claire.co.uk

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

3.2 Towards implementation Co Molenaar, VROM NL, Hans Slenders, ARCADIS, NL and Paul Bardos, r3 Environmental Technology Ltd, UK The obvious starting point for implementation is for all those involved to have a common understanding of what ‘sustainable remediation’ actually is. While this was the objective of the other syndicate group, the ‘implementation’ syndicate identified a number of key requirements for any definition: • the goal of remediation should be risk management, now or in the future; • sustainability expresses a balance between environmental, economic and social objectives; • there are ‘narrow’ objectives related to the drivers for a particular project, and ‘wider’ objectives related to its consequences for the environment, economy and society as a whole;

Figure 13. Groundwater infiltration and extraction schematic for the Strijp site system

• any definition must consider a series of ‘boundaries’ to ensure that like is compared with like.

The key implementation needs

The framework should be adapta-

These boundaries include the

began with a requirement for lead-

ble to changing circumstances in the

system being considered, spatial

ership from some entity – leader-

future (such as climate change). It

and temporal boundaries, and

ship with an inspirational approach.

should also be simple.

life-cycle boundaries, as set out

It was felt that this need was an

in Table 3;

urgent one. Implementation would

A series of tools are needed to

• the land-use context plays a

not be easy unless the agreed con-

engage stakeholders and support

major role in determining

cept and implementation approach

consensus-based decision-making,

sustainability of site reuse, and

for ‘sustainable remediation’ was

which is an integral part of sustaina-

sustainable remediation is a part

agreeable to the different stakehold-

ble development; and these should

of this, as it is a part of the soil-

ers involved in the contaminated-

be supported by a demonstration

functionality debate.

land management sector. Prefera-

and validation programme.

bly, any sustainable remediation Implementation issues were then

framework would be consensus-

The barriers to the implementation

discussed in terms of ‘needs’ and

based from the ‘bottom up’, rather

of sustainable remediation include

‘barriers’.

than imposed from the ‘top down’.

the current divergence in ideas of

400

Clean-up & regeneration bulletin

Table 3. Sustainability appraisal boundaries1 Life-cycle

Life-cycle boundaries consider how far the option being considered should be broken down into sub-units requiring some sort of analysis. A key part of understanding life-cycle boundaries is the concept of cradle to grave or indeed cradle to cradle.

System

The system boundary describes the ‘edges’ of the system being considered, i.e. where it interfaces with the surrounding environment, society or economic processes or other systems: e.g. the scope of the project and its operations.

Spatial

The intuitive understanding most people have of geographical boundaries is a site perimeter. However, the sustainability appraisal has to consider impacts and benefits across the system and life-cycle. These may occur: at the site being remediated; at other sites (for example, treatment centres); at supplier sites (including how a project approach might affect waste collection); in relation to transportation and distribution; and due to distant impacts, for example, effects on air and water, or increased traffic. For some appraisal purposes it may be appropriate to distinguish between local and distant effects.

Temporal

The initial time boundary is the commencement of the operations defined by the system boundary,2 The remaining time boundary is of course the point in time beyond which effects are no longer considered.

1. Summarized from: Sustainability Appraisal for the Use of Compost-Like Outputs – A Simple Qualitative Approach (in prep.) Bardos, Chapman et al. r3 environmental technology Limited. www.r3environmental.com; and Bardos et al. (2000) Assessing the Wider Environmental Value of Remediating Land Contamination. Environment Agency R&D Technical Report P238. http:// publications.environment-agency.gov.uk/epages/eapublications.storefront/47ff753701080170273fc0a80296060d/Product/View/ STRP238&2DE&2DE. 2. Conceptualization, design, delivery, construction, utilization, production, refurbishment and maintenance, decommissioning, etc.

what sustainability is in the context

or comparison. The final barrier is

There is now a general acceptance

of remediation. In addition, the

of course the identification and

that the aim of remediation is the

rigid regulatory contexts affecting

engagement of those who ought to

control of risks to human health and

many projects are a significant

be interested, and the removal of

the environment, whether a project

obstacle to the selection of a sus-

‘professional blinkers’ by all, to ena-

is driven by a development need, a

tainable approach, and tend to

ble a more holistic vision.

regulatory need or a corporate need such as a merger or acquisition. Fol-

make conventional approaches easier to adopt: there is insufficient

4 Discussion

‘regulatory space’ for sustainable

lowing Brundtland, countries have elaborated detailed sustainable

remediation. Technical implemen-

This discussion has been drawn

development policies. The ‘sustain-

tation is difficult while there

from the discussions in the work-

able remediation’ debate is that

appears to be no strategic approach

shop, including its closing plenary

these risk-management actions

to the management of subsurface

session, and from comments kindly

(remediation) must themselves

processes and systems, and no

sent in by a number of delegates and

constitute sustainable develop-

agreed ways of considering the vari-

SAGTA/NICOLE members after the

ment. For example, in somewhat

ous boundaries to any assessment

workshop.

simplistic terms: is the removal of 100 g of diesel-range hydrocarbon from a tonne of soil sustainable if

Sustainable Remediation Considerations

litres of non-renewable fossil fuel have to be expended and CO2 subsequently produced? This debate is summarized in Figure 14.

“Good” environment

“Bad” environment

The NICOLE/SAGTA workshop

Once upon a time the journey was enough

arrived at the following description

Now we have to take a sustainable route as well

of sustainable remediation: a

Figure 14. The sustainable remediation context cartoon (from NICOLE London Workshop Report)

401

‘framework in order to embed balanced decision making in the selec-

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

tion of the strategy to address land

three key elements of sustainable

resource impacts (such as life-cycle-

(and/or water contamination) as an

development.

based tools, carbon footprints/

integral part of sustainable land

intensity and cost–benefit analysis).

use’. Any definition must allow the

This description is not yet a defini-

However, such quantitative tools do

ability to:

tion, but rather describes a process

not express the full scope of dimen-

to arrive at sustainable remediation.

sions of sustainable development

• make risk-based decisions;

While the concept of sustainability

(see Box 1), and as such will not

• consider (and define) boundaries

is founded in the Brundtland report,

address a range of wider sustainable

there are differences in its interpre-

development considerations – from

tation in the context of soil remedia-

soil functionality to ‘inclusiveness’

tion. Key areas of debate include the

in decision-making. There was sup-

following points.

port for a tiered approach, which

in time and space; • ensure a balance of outcomes can be achieved; • consider land (and water) use

began with simple indicator-based

first as part of the process. Technical people tend to like meas-

qualitative tools, with quantitative

The key elements behind this

urable and quantifiable things. The

tools used only where these simpler

approach are as follows. The basic

Brundtland concept can be seen as a

tools could not reliably distinguish

decision-making rationale behind

little woolly to be used in a quantita-

between options, or where there

contaminated land management

tive comparison of risk-manage-

was serious disagreement between

has a basis in risk assessment. How-

ment options. A number of

stakeholders. This was also seen as a

ever, the method of achieving risk

delegates preferred a concept that

means of reducing the costs and

management must in itself not place

was more limited in scope than

complexity of decision-making.

unreasonable demands on the envi-

Brundtland, focusing in particular

There was a clear message that ‘sus-

ronment, economy and society – the

on measurable environmental and

tainability is more than carbon’, and

Box 1. Dimensions of sustainable remediation Sustainable remediation takes a holistic view and seeks a balanced approach to risk management. This is a multi-dimensional consideration, illustrated in Figure 15. Figure 15 is a representation of two remedial options: ‘blue’ and ‘red’. Both options have the same ‘core’ risk-management benefit, but each has different overall economic, environmental and social values, and hence different sustainability. Each ‘value’ is, of course, a composite of a number of individual ‘indicators’ of sustainable development which may be collated in a generic sense, or based on an existing sustainable development indicator set.

economic ec2 s2

ec1

ev2 so2

so1

social

Figure 15. Simple comparison of ‘sustainability’ for two different remediation options

402

ev1

environmental

Clean-up & regeneration bulletin

scepticism about the usefulness of

grounds might hold widely varying

appraisal, the methods used to

generalized metrics for remediation

views about particular individual

achieve them.

technologies, such as €/m2

indicators of sustainability. As such

or kg

carbon per kg contaminant

subjectivity appears to be unavoida-

removed.

ble, it should be explicitly catered for in appraisal tools, and it should

Effectively, a lot of discussions centred on which systems are being compared. For example, remediation may be a component part of a larger redevelopment project – should a separate sustainability appraisal of the remediation step be undertaken in this situation? Some felt that it was unnecessary, as the major sustainable development decisions and impacts were at the level of the redevelopment projects. Others felt that redevelopment was not the only driver for risk management, which in itself should be intrinsically ‘sustainable’, and that it would be invidious to treat (say) risk-management activities in relation to ongoing facilities in a different way to risk-management activities for sites being redevel-

be made transparent to all users. Sustainable development will be a consideration affecting remediation work at more than one level, for example, policy supra-national, national, regional or local levels, and at different project levels: for example, an entire remediation

It was also suggested that sustainability might be a parallel consideration at more than one level, for example: selection of the risk-management approach for a particular characterized and agreed problem site; for a redevelopment project requiring risk-management works as a component; across a municipality or other such local area; and as a part of regional, national or supranational policy.

project versus the remediation seg-

It was also widely suggested that

ment; or an entire river-basin man-

NICOLE should adopt a leadership

agement project versus mitigating

position in establishing and devel-

problems at one particular site.

oping a sustainable remediation

What is seen as constituting sus-

debate across Europe, and as such,

tainable development may be differ-

through continuous support and

ent at these different levels, and, not

feedback, it needed to link with the

only that, but decisions taken at one

pioneering work now being under-

level affect the available options at

taken by CL:AIRE through its

another. Therefore sustainable

SURF-UK initiative.

remediation cannot be defined if the context is not first defined.

Acknowledgements NICOLE and SAGTA gratefully acknowledge:

oped. Another point, raised several

5 Concluding remarks

•

should be modifiable in the light of

NICOLE and SAGTA consider that a

•

sustainability assessments.

risk-management approach to land

times, was to ask whether risk-management objectives themselves

contamination management should Another issue raised was the role of

be viewed as a given. From the view-

subjectivity in sustainability

point of defining sustainable reme-

appraisal, for example in valuation

diation, therefore, sustainability

processes, or where ‘weightings’ are

criteria needed to be taken into

used in qualitative assessments.

account in both setting the goals

Stakeholders from different back-

and, through appropriate options

•

the speakers and chairpersons for their contributions to the workshop and their comments on this report; the members of the organizing committee: Paul Walker, National Grid Property/ SAGTA chairman; Ruth Chippendale, Shell/SAGTA vice-chairperson; Doug Laidler, SAGTA secretary; Markus Ackermann, DuPont/NICOLE Industry; Hans Slenders, Arcadis/NICOLE service providers; Marjan Euser, NICOLE secretary; English Partnerships for hosting this event; and CL:AIRE for facilitating the event.

Clean-up & regeneration bulletin

Volume 16 Number 4 October 2008

Gauging the impact of the Environmental Liability Directive

In this issue

Simon Boyle outlines the potential effects of this long-awaited legislation.

Policy / regulation Clean-up / regeneration Companies / bodies International Research

405 407 411 412 415

With the final Regulations aiming to

operating in Europe, as it uses

be implemented by December

strong financial incentives for

liable to restore any biodiversity

2008, the Environmental Liability

landowners and operators to

damaged by the incident for which it

Directive (ELD) signals a new

protect the environment. These

was responsible. This could mean

approach to environmental

incentives largely rest on legal

any harm caused to protected

responsibility for commercial

liabilities and subsequent costs that

species, natural habitats and sites of

landowners. The aim of the

could result from any

special scientific interest.

Directive is to prevent

environmental damage. A mix of local authorities, the

environmental damage occurring, as well as forcing companies to

The ELD intends to be both

Environment Agency and Natural

compensate for any harm caused on

preventative and remunerative. It is

England will police the regulations.

their land. The Directive has been

aimed at encouraging operators to

If environmental damage does

well documented in the past decade,

avoid environmental damage, but if

occur, then the onus will be on the

but there is still confusion about

damage is ever caused, then the

operator to alert the regulators and

how it will affect everyday practice.

ELD is also intended to force people

take action to immediately limit the

to admit to the accident and

effects. The regulator will then liaise

remediate for any such damage.

with the landowner to make sure the

The ELD has gone a step further

necessary action takes place.

than other liability schemes In the past, if a company had an

Similar rules will apply to an

incident that damaged the

impending threat of contamination.

environment, then the main threat of financial liability would be the

Previously, when enforcement

possibility of a civil claim for

responsibility in the Environmental

damages from a neighbour, and

Protection Act has been shared

potentially prosecution. However,

amongst different regulators, it has

securing a successful civil claim for

led to problems, often because of

damage is uncommon, as there are a

lack of technical understanding

number of well-worn legal defences

amongst all parties or of financial

against such a claim.

resources. This will hopefully change under the ELD, as it states

Simon Boyle is legal director of environmental consultants Argyll

This will change once the ELD is

that anyone who has a sufficient

implemented. For the first time in

interest can initiate action by

English law, the landowner may be

notifying the authorities. This is

405

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

good news for NGOs, who often it means they will be able to report

Study recommends NLUD review

instances of environmental damage

The way in which local authorities

to the regulator.

identify and assess land for future

have a keen interest in this area, and

redevelopment could be

www.nlud.org.uk www.kingston.ac.uk

Revised nitrate regulations and maps published

Whilst the ELD was going through

transformed, due to advances in

New regulations will extend the

its various draft stages, there was

technology and changing

areas of England designated as

much discussion about the issue of

information needs, according to a

Nitrate Vulnerable Zones (NVZs)

environmental insurance. An initial

study of the ten-year-old National

from 55% to around 70%.

suggestion was that there should be

Land Use Database of Previously

compulsory insurance for operators

Developed Land (NLUD-PDL).

This reflects the Government’s decision to continue designating the

of high-risk activities, but the composite insurers lobbied against

Recommendations for the review of

zones on a selective basis rather

this, and instead a much weaker,

NLUD were commissioned by

than adopt the whole-territory

general encouragement to insurers

English Partnerships and produced

approach of some EU Member

to develop suitable policies for ELD-

by researchers at Kingston

States.

related liabilities was introduced.

University.

The Regulations also make changes

Nonetheless, the specialist insurance market is responding to

The research looked at the need for

the challenge and the opportunities.

brownfield data; possible

A prudent operator would do well to

improvements to NLUD; and the

check the available insurance

needs of a wider audience for

policies and to see which provides

information of this kind. The

best value and express coverage for

recommendations include:

ELD liabilities. • NLUD-PDL site records should Involving a specialist

be converted from points (single

environmental consultant as an

x, y coordinates) to polygons

integral member of the team right

(site boundaries);

from the planning stage can

• records should be more

minimize the cost of complying with

compatible with existing local

the new regulations and prevent any

land and property gazetteers;

future legal action. You can ensure

• the database should be publicly

that you receive a comprehensive

accessible online, and

environmental assessment by

maintained in real time by online

checking your consultant is fully

updates direct from local

compliant in Part 2A of the

planning authorities;

Environmental Protection Act as well as the ELD. Argyll Environmental is currently developing reports to help businesses manage potential risks

• records on developed sites

to the Action Programme, specifying actions which farmers in NVZs must take to reduce and prevent nitrate leaching and run-off to waters from manures and fertilizers. Changes to the Action Programme will come into force on 1 January 2009, although some of the Action Programme measures have a grace period for compliance of up to three years, to allow farmers time to make adjustments to their farming practices, or capital investment such as storage facilities. The main changes in the revised Action Programme relate to: • a whole-farm limit of 170 kg per

should remain on the database to

hectare for nitrogen from

inform future decisions on

livestock manures, which applies

development, and as part of a

to all land (currently grassland

national archive;

has a limit of 250 kg). The

• the database structure should be

Government has previously

under the ELD. For more

more flexible to accommodate

confirmed that it will pursue a

information, please visit

future changes in planning

derogation from the European

www.argyllenvironmental.com

policy.

Commission on this limit;

406

Clean-up & regeneration bulletin

market downturn, according to this

Historically, industrial properties in

organic manures, which will be

year’s IPD Regeneration Index. The

regeneration areas have

longer and will apply to all soil

Regeneration All Property total

consistently offered investors

types;

return fell to –6.0% in 2007,

strong returns and come with a

compared with IPD’s broader UK

lower degree of risk. However, in

requirements, which have been

All Property Index, which slid

2007, industrial properties in

amended to reduce the risk of

–3.4% over the same twelve-month

regeneration areas slightly

manures being spread when

period. This year, for the first time,

underperformed, earning investors

conditions are unsuitable; and

the index looked at development

–4.4% compared with a UK average

performance in regeneration areas.

of –3.5%.

• closed periods for spreading

• manure storage capacity

• the introduction of forward planning rules to ensure nitrogen

Developments in regeneration areas

applications from manures and

returned 1.2% in 2007,

fertilizers are more accurately

In the retail sector, retail

outperforming the IPD UK All

directed to crop needs.

warehouses and shopping centres in

Property index.

regeneration areas underperformed the retail-warehouse and shopping-

Maps showing the revised areas will be available via the OPSI and Defra

Over the medium and longer term,

centre UK averages, returning

websites, and at http://

total returns from regeneration

–7.5% and –4.7% respectively.

nvz.adasis.co.uk/maps. Farmers

areas are identical to the broader

will have until 31 January 2009 to

UK as a whole. The last 27 years

Yolande Barnes, research director

lodge an appeal if they believe their

have shown average annual total

at Savills said: ‘The case for

land has been wrongly designated.

returns of 11.0% in both cases. The

investment in regeneration assets is

last ten years show 11.4% total

more compelling if residential

returns on the IPD All Property

property and development activity

Index and 11.3% on the

are included. In fact, the more

Regeneration Index. It is only in the

exciting returns and possibly the

A £6m package to help bring

last three years that regeneration

more stable income streams have

contaminated land back into use

properties have under-performed at

been enjoyed by those willing to

was announced by Environment,

8.8%, compared to 10.8% for All

diversify away from standard, “big

Sustainability and Housing

Property.

box” commercial standing property

£6m for brownfield sites in Wales

Minister Jane Davidson in July.

investments and towards

The available funding – £2m a year

However, different property sectors

over three years – will go to local

in regeneration areas showed

authorities and the Environment

different patterns of returns.

residential “small box”, “neighbourhood commercial” type properties and development activity.’

Agency for projects across Wales. They will use it to investigate and take remedial action at contaminated land.

Offices managed to retain their attraction in relative terms,

Clean-up / regeneration

returning –0.9% in regeneration

Abingdon contract award

areas, as compared to –0.5% in the

Heijmans Blackwell Remediation

‘Regeneration areas more vulnerable in short term’, IPD finds

broader UK index.

Total returns for office property in

the former Exxon Mobile research

Regeneration properties are still a

regeneration areas have

centre at Milton Hill, Abingdon. The

solid option for investors looking for

consistently exceeded the IPD UK

main contractor is Masterton

long-term returns, but have proved

average over the last five and ten

Demolition, which has cleared the

more vulnerable to the recent

years.

site to ground level, and exposed the

has won a bioremedation and groundwater treatment contract for

407

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

area of contamination below the former barrel store. HBR is responsible for the excavation and processing of 16 000 m3 of made-ground and weathered mudstone. Parsons Brinkerhoff is the client’s environmental consultant, and ABB is the project manager. Work commenced in June and is due for completion in October 2008. Heijmans Blackwell Remediation Ltd has also been awarded a contract to carry out groundwater

Work at the former Ebbw Vale steelworks

remediation in a busy area of East London. The works will comprise the installation of 40 deep vertical wells and two horizontal wells positioned within the River Terrace Gravels. The operations are designed to reduce the ammonium from the minor aquifer over a period of one to five years.

new roads have a 25% recycled

Leighton Andrews, the Assembly

content.

Government’s Deputy Minister for Regeneration, said that when the

The strategy also requires that Site

final phase of the £25m reclamation

Waste Management Plans

programme is completed, more

(SWMPs) are used to monitor,

than two million tonnes of materials

reduce and recover more waste

will have been excavated,

during the design and construction

remediated on-site and reused.

phases. WRAP’s (Waste &

Welsh Steelworks sets targets for resource efficiency The Works, the former Ebbw Vale steelworks site, is a £300m venture

Resources Action Programme) Net

The Ebbw Vale Steelworks closed in

Waste Tool will be used by the

2002, and was demolished and

project team to prioritize cost-

decommissioned by Corus in 2004.

effective ways of meeting the

Reclamation of the site, including

recycled content and waste targets.

decontamination work, capping of mine shafts and re-engineering of

being undertaken by the Welsh

As part of its waste minimization

Assembly Government in

unstable slopes, began in late 2005.

and recycling strategy, the project is

partnership with Blaenau Gwent

Halcrow Group Ltd is the

also using quality compost to

County Borough Council. It will

engineering consultant and

regenerate the site and is the first

bring a community hospital,

Edmund Nuttall is the principal

project in Wales to take part in

learning campus and around 270

contractor for the current phase of

WRAP’s trailblazer programme.

reclamation works.

The 185-acre site is using up to

For more information on BSI PAS

new dwellings, as well as a new business hub, to the centre of the Ebbw Vale valley.

15 000 tonnes of compost certified

100 compost on the Net Waste Tool,

to BSI PAS100, which is being

visit www.wrap.org.uk/

The project’s sustainability strategy

mixed with existing subsoils and

composting and

includes a requirement that all new

colliery spoil to create new topsoils

www.wrap.org.uk/nwtool.

buildings must have a minimum of

capable of supporting woodland

15% recycled content and that all

and grassland habitats.

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Clean-up & regeneration bulletin

programme to address a complex mixture of site contamination across a variety of media, thus unlocking this heavily polluted site. Located on the former Delta Metals engineering facility, this 4.4-ha site was heavily contaminated during over 60 years of heavy industry associated with the machining and manufacture of vehicle components for the car industry. The site is located in the shadow of Spaghetti

Thames clean-up

Junction, an area of former heavy industry, located above a major

Thames clean-up

Briefing Remediation Innovation

aquifer (Sherwood Sandstone) and

Over five tonnes of refuse were

Awards, in the category of ‘Best Use

adjacent to the River Tame. Whilst

removed from the banks of the

of a Combination of Remediation

historically impaired, these water

River Thames in August in the River

Techniques’, at the recent

resources form the most sensitive

Clean-Up Challenge. The initiative

Contaminated Land & Brownfield

environmental receptors in the

was facilitated by the Jones Lang

Remediation Conference in

area, together with the future site

LaSalle Management Services team

London.

occupants of the proposed industrial facilities (commercial

in partnership with Thames 21. 2008 sees the completion of the

use). The site was underlain by

Occupiers from Hermes’ Central

Meteor Park Development located

mainly granular made-ground, in

London Offices portfolio were

to the north of Birmingham. The

turn overlying organic alluvial clays,

encouraged to participate, and

site was purchased by SEGRO Plc,

river terrace sands and gravels

companies including NBC

formerly Slough Estates, and was

under which lies the sandstone

Universal and Barnett

designated for demolition and

aquifer. Independent water bodies

Waddingham LLP took up the

redevelopment into four large

were found in the made-ground, the

challenge, as well as representatives

warehouse facilities ranging in size

terrace gravels and the sandstone

from Hermes, Upstream

between 2066 and 10 690 m2. The

aquifer.

Sustainability Consultants and a

site was identified by SEGRO as

number of Jones Lang LaSalle staff.

prime for development, being in

Various site investigations,

A team of 34 spent a morning

close proximity to Birmingham city

undertaken prior to WSP

clearing some five tonnes of refuse,

centre and major transport routes.

Remediation’s involvement,

including scrap metal, fencing and

However, prior to WSP

identified the following

lorry tyres, from the banks of the

Remediation’s involvement,

contamination:

Thames at London Yard on the Isle

development was becoming

of Dogs.

marginal because of spiralling

• diesel- and lubrication-oil

remediation costs associated with

hydrocarbons and chlorinated

significant site contamination. In

EHC® site submitted for remediation technology award

solvent contamination of made-

delivering this project, WSP

ground and alluvial soils;

combination of sustainable on-site

product present as light non-

EHC has been included in an

treatment technologies, integrated

aqueous-phase liquid (LNAPL)

application for the 2008 Brownfield

within a challenging construction

within perched water and sands

Remediation has adopted a

409

• localized hydrocarbon free

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

and gravel aquifer associated

method for treating organic

enhanced reductive conditions

with former below-ground

contamination. Programming

could be established, in order to

structures;

constraints meant that the soil

accelerate reductive dechlorination.

remediation works would largely be

The product chosen was Adventus

undertaken during the winter, and

EHC™, a formulation of carbon and

so aerated biopiles were selected to

zero valent iron with added

reduce the sensitivity of the

nutrients, designed to provide

treatment works to adverse weather

support for and to accelerate the

conditions. The feasibility trials

action of the indigenous bacteria

included soil sampling and

within the groundwater and

laboratory analysis to examine soil

saturated zone. The company says

condition in relation to

this technology is currently the most

contaminant speciation; sampling

advanced reductive groundwater

nutrient content to identify the key

bioremediation.

• widespread dissolved-phase chlorinated solvent contamination within the underlying sands and gravel aquifer. The mix and spread of contamination throughout the soil and groundwater profile meant that a combination of remediation techniques would be required. The methodologies adopted comprised best practice, using sustainable onsite treatment technologies within a compressed remediation

bioremediation drivers; bacterial plate counts to assess natural

‘Green remediation’ focuses on the

bacterial activity; and physical

remediation technologies

screening to assess treatability.

employed, the objectives of the remediation scheme, and the

programme, and supported by

impact of the remediation works

remediation design trials, risk

Groundwater treatment trial –

assessment and validation

prior to WSP Remediation’s

protocols. The remediation works

involvement, the preferred

were initiated by completion of an

remediation method for dealing

extensive supplementary site

with the groundwater

investigation followed by a site-

contamination had been

specific quantitative risk

containment, incorporating

assessment (QRA). The

treatment via some form of

supplementary investigation works

permeable reactive barrier (PRB)

enabled further delineation of the

and a funnel and gate system.

contaminant source zones, and the

Discussions with the EA identified

QRA was based upon a CONSIM

potential concerns associated with

model using a high percentage of

this strategy, given the extent of the

site data to minimize the

contamination (too significant); the

requirement for generic

absence of a demonstrable aquitard

assumptions and to give confidence

for any wall to ‘key’ into; and the

to all parties that the risks had been

long-term efficacy of a containment

adequately characterized.

strategy, given the potential for

Remediation trials were carried out

vertical migration of the solvent

to fine-tune the remediation design,

contamination into the underlying

optimize the remediation

aquifer. Step- and continuous-rate

techniques applied, and recover

pump tests were undertaken to gain

(other than drilling

site-specific data for the risk

a greater understanding of the

equipment, delivery of

assessment model.

aquifer’s flow characteristics. Trial

product and site

injections of a saline solution were

against the environmental improvement achieved by the works. What defines ‘green remediation’, as opposed to ‘sustainability’, is a reduced emphasis on seeking to quantify wider intangible social benefits, though some will accrue, for example, by better carbon management. The Meteor Park site is put forward as an exemplary ‘green remediation’ project, for the following reasons: • The solvent treatment by direct injection of EHC™ (reductive dechlorination) involves: – in situ destruction of pollutant mass; and – limited energy consumption

attendances). • The soil remediation by static

Soil treatment trial – ex situ

carried out to determine zones of

bioremediation was chosen as a

influence, followed by the injection

aerated biopiles:

well-established and successful

of a reducing substrate to check that

– avoids removal of

410

Clean-up & regeneration bulletin

contaminants and soils to

efficiency of our clients’ mapping-

support, providing habitats for

landfill, relieving the waste

related projects.’

some of the UK’s most notable, yet threatened, aquatic species.

burden; – involves limited plant biopiles, with some diesel

Lancaster University acquires mobile laboratory

consumption required for air

Lancaster University’s Centre for

generation and blowers;

Sustainable Water Management

Health Protection Agency develops response to large chemical incidents

– reduces contaminants by up

(CSWM) has acquired a mobile

The Health Protection Agency has

requirements for static

to 80%.

laboratory designed and

Note: some carbon dioxide is

constructed by Partech

generated as part of

Instruments.

developed an environmental sampling process to help assess the risks to human health from major

degradation process

chemical disasters. There is

(unavoidable and embedded

The mobile laboratory will play an

currently no single UK agency

within the pollution mass).

important role in research into

responsible for environmental

understanding how nutrients move

monitoring of surface soils and

between ground- and surface

herbage for the purposes of health-

waters.

risk assessment following a major

Companies / bodies Mouchel introduces corporate mapping system

incident involving the release of The mobile laboratory contains two

noxious chemicals. The Agency has

Mouchel has installed a new group-

four-channel nutrient analysers and

built on its existing sampling

wide mapping system called

a water-quality monitor. These

capacity for radioactive

maps@mouchel. The new web

instruments enable water quality,

contamination to develop teams

portal will allow Mouchel to

i.e. turbidity, pH, redox, DO, and

capable of collecting soil and

centrally manage and distribute

conductivity, to be measured every

herbage samples after the fallout

Ordnance Survey datasets and

ten minutes. If the turbidity level

from large chemical incidents. The

licences, bringing an improved

increases, then the total phosphorus

Agency can now respond to a major

service delivery to its clients.

facility is turned on automatically to

chemical disaster by deploying up to

measure in fast total phosphorus

20 scientists to gather data on

The new approach was designed by

ten-minute cycles. The laboratory is

environmental contamination from

Mouchel’s land information

solar- and wind-powered, and

a range of inorganic and organic

management business

results are transmitted by

chemicals. Several different types of

LandAspects, in partnership with

telemetry.

sampling kit can be used to ensure

Bristol-based software company

that the samples are properly

Innogistic. It is said to be the first

‘The mobile laboratory supplied by

collected for laboratory analysis.

system in the UK to combine map

Partech Instruments Ltd will play

Agency scientist Andrew Kibble

licensing and data management for

an important role in research into

said: ‘This capacity allows the

a large organization.

understanding how nutrients move

Agency to have its own in-house soil

between ground and surface (river)

and grass sampling capacity.

Mouchel business unit director

waters,’ comments Dr Paddy

Procedures have been developed

Mark Hurley said: ‘Being able to

Keenan at the CSWM. ‘To put the

that provide sampling guidelines for

centrally manage geospatial

significance of this research into

our monitoring teams which will

information is an increasingly

context, groundwater-fed rivers,

enable them to sample the right

common request for new contracts,

such as the one the mobile

locations, at the appropriate

particularly those in the public

laboratory will be monitoring, are

frequency to ensure the effective

sector. Utilizing maps@mouchel

very important because of the

assessment of potential sites

will enable us to improve the

special ecosystems that they

following major chemical incidents.’

411

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

that utilizes the aggregate and soils

Colorado Department of Public

that are already in the ground. It

Health and Environment and US

mixes them with a binder – either

EPA. The site and surrounding area

Eco Foundations will offer the deep

cement (dry or wet), pulverized fuel

will be used in the future for

triple auger soil-mixing system for

ash, lime or other powders – and

recreation and as wildlife habitat. A

in situ wet and dry soil stabilization.

makes concrete in situ, either in

portion of the site will be

Using machinery from German firm

columns or over large areas. You are

transferred to the US Department of

RTG, the triple auger system is

therefore not taking the ground

Energy for long-term management.

fitted to a telescopic leader rig and

away as you would in traditional

creates a panel of three 550-mm

piling methods; you are using what

An early mill on the site provided

soil-mixed piles in one insertion of

is already there and thus reducing

radium for Marie Curie’s research.

the paddles. The wet-soil mixing

waste; there are less aggregate costs

In 1942, the US Army Corps of

system has a computerized

and the need for landfill is also

Engineers built facilities to process

monitoring system to record

reduced.’

uranium in Uravan, and during the

New company launched to market soil-mixing technique

everything – from the mix being injected, to the volume of cement

www.eco-foundations.co.uk.

slurry against depth of penetration

1940s the mill processed uranium for the Manhattan Project. Later, uranium produced from the Uravan

and inclination of the panel, giving a

International

mill was used to fuel nuclear power

comprehensive QA as-constructed

Clean-up of Uravan uranium mill completed

plants.

report. The same system can also be used with dry-soil mixing systems to introduce binder into soft soils to improve stability. The same triple auger system can be used to install cement, lime or blast-furnace slag to mix with the existing soils for ground improvement.

A chapter in the history of the uranium industry in western Colorado closed when the US Environmental Protection Agency (EPA) certified the completion of the 20-year clean-up of the Uravan Mill Superfund Site.

Historic mining and milling at Uravan included the production of radium, vanadium and uranium. The site was contaminated by radioactive residues resulting from the processing of vanadium- and uranium-containing ores from the early 1900s through to the mid-

Uravan, a former uranium and

1980s. From the time that Uravan

vanadium mine and processing site

began operating in the 1920s until it

Mass soil stabilization is also

located on the San Miguel River,

was shut down, the mill processed

available using an excavator-

had long been contaminated with

over ten million tons of uranium-

mounted rig that mixes binder with

radioactive residues, metals, and

vanadium ore. During this time,

extremely soft soils such as peat and

other inorganic materials. The 680-

operations produced in excess of ten

alluvium to turn previously

acre site dates to the dawn of the

million tons of tailings; 38 million

unusable flooded marsh-type areas

atomic age, and its closing coincides

gallons of waste liquid residue; and

into solid ground.

with renewed interest in uranium

other milling wastes containing

mining and milling in the area.

radioactive materials, metals, and

Eco Foundations MD, Robert

Umetco, a subsidiary of Dow

McGall, said: ‘The triple auger soil-

Chemical, has operated the facility

mixing system is suitable for sea

since 1984.

inorganic contaminants. The clean-up effort removed more

defence work, flood protection and

than 13 million cubic yards of mill

cut-off walls, retaining walls and

The Uravan mill site was designated

tailings, evaporation pond

cofferdams and ground

a Superfund site in 1986, and clean-

precipitates, water-treatment

strengthening for roads and

up took place from 1987 to 2007.

sludge, contaminated soil, and

railways, to name but a few. Our

Clean-up work was performed by

debris from more than 50 major

new process is a soil-mixing system

Umetco, with oversight from the

mill structures on the site. These

412

Clean-up & regeneration bulletin

wastes were collected and disposed

the space programme since the

contact) was chosen as a more cost-

of in four on-site disposal cells. The

early 1960s. Leaks from a 4000-

effective means of site remediation.

cells also contain wastes from a

gallon underground fuel-oil tank,

Most conventional in situ chemical

nearby abandoned mill in Gateway,

subsequently decommissioned and

oxidation chemistries were ruled

Colorado, and mill tailings from the

removed, led to notable

out, however, due to their

Naturita millsite. In addition, more

contamination of soil and

corrosivity and tendency to

than 380 million gallons of

groundwater, including a layer of

generate intense heat and/or

contaminated liquid, collected from

light non-aqueous-phase liquid up

explosive pressures.

seepage containment and

to 15 in thick, with total recoverable

groundwater extraction systems,

petroleum hydrocarbon (TRPH)

Considering the challenges posed

were treated at the mill site. The

levels as high as 20 000 parts per

with the potential use of

clean-up cost more than $120m.

million (ppm) in soil and 42 ppm in

conventional chemical-oxidation

groundwater.

chemistries, Tetra Tech proposed

In situ chemical oxidation for subsurface soil and groundwater remediation

RegenOx™, a non-corrosive, lowThe tank and 178 tons of readily

temperature, low-pressure

accessible contaminated soil were

chemical oxidation technology,

excavated and properly disposed of

developed by Regenesis. RegenOxTM

The National Aeronautics and

early on, but other, harder-to-reach,

is a two-part product which includes

Space Administration’s Kennedy

contaminated soils had to be left in

an alkaline oxidizer powder and a

Space Center in Cape Canaveral, has

place beneath and near building

liquid activator. When combined,

undertaken aggressive groundwater

foundations, where essential

they produce a cascade of chemical

and soil remediation to treat an area

underground utilities were located.

oxidation reactions that effectively

of on-site petroleum hydrocarbon

Although Tetra Tech’s engineering

destroy a range of contaminants but

contamination. NASA and its

evaluation identified excavation as

do not pose a destructive risk to

consultant Tetra Tech were faced

the preferred approach for

subsurface infrastructure and other

with the challenge of removing the

remediating the remaining

equipment.

contamination while maintaining

contamination, the cost of

the integrity of underground

excavating the hard-to-reach soils

utilities, piping, and infrastructure.

was prohibitive, at over $1m. After

50 000 pounds (137 000 gallons) of

examining alternative remediation

RegenOxTM into the site via 52

The Launch Equipment Shop, part

technologies, in situ chemical

injection wells. After treatment, the

of NASA’s Vehicle Assembly

oxidation (the application into the

area of TRPH-impacted soils was

Building complex, has conducted

subsurface of highly reactive

reduced to approximately one-

highly specialized manufacturing,

chemicals, which chemically oxidize

quarter of its original size. Site-wide

fabrication and assembly work for

and destroy contaminants on

groundwater contaminant

Tetra Tech injected approximately

NASA’s Vehicle Assembly Building (left), about 400 yards from Launch Equipment Shop, was the world’s largest building when completed in 1962-65. Tetra Tech used re-injectable wells (left and centre) to emplace RegenOx™ into contaminated soil and groundwater behind the LES. The right-hand photo shows RegenOx™ oxidizer and activator components after blending into an appropriate volume of water and ready for insertion into the subsoil.

413

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

concentrations of TRPH were also

He said it is possible that the

centuries of natural decay, this

reduced substantially, and the

construction of this new agro-

process will cut the time to 20 to 40

thickness of the free-product layer

industrial sector could result in

years.’

was reduced by 80%. The

radioactivity being removed from

programme originally included a

50 000 km2 of land within 20 to 40

Greenfield plans a multi-fuels

more costly soil-removal phase to

years, rather than the centuries

refinery at Mozyr, Belarus,

address the free product

which natural decay would take.

producing 550 million litres of

contamination; however, after further investigation, the

ethanol annually, along with Speaking at a conference organized

biodiesel, biogas and electricity.

by Greenfield Project Management

Each stage can use waste from the

handle the phase-separated

Ltd, which plans to build a multi-

previous stage, along with fresh

material.

fuel biorefinery in Belarus to

biomass feedstock. Initially, the

www.regenesis.com

produce bioethanol, biodiesel,

fuels will use feedstock such as

biogas and green electricity, Mr

sugar beet and oil-bearing plants

Savinykh said his government

from clean land, but, following field

would rapidly complete the

trials and safety design, all facilities

planning phase by the end of 2009,

will begin using contaminated

and that he hoped implementation

crops.

RegenOx

dosing was adjusted to

‘Biofuels sector is key to cleaning up Chernobyl’ Belarus is to construct a huge

would begin in 2010. Existing technologies will be

biofuels sector in an effort to finally rid its territory of the radioactive

Saying that the government of

applied to remove all radioactivity

contamination which still remains,

Belarus was ‘fully committed’ to the

from the final products and from

26 years after the nuclear reactor

Chernobyl Bio-clean Programme,

any effluents and emissions, leaving

exploded in Ukraine, near its border

he stressed that the agricultural

small quantities of radioactive

with Belarus.

production cycle in the affected

waste to be stored in safe facilities.

territories was unable to remove A senior Belarus diplomat told a conference in Brussels in September that his country’s number-one priority is to decontaminate the lands affected by the Chernobyl nuclear disaster, and that it will pursue this aim by building up a giant biofuels sector.

radionuclides via the cycle of ‘planting/harvest/process/food’. Even though plants absorb radioactive particles such as

US EPA identifies contaminated sites for renewable energy production

caesium 137 and strontium 90,

Using Google Earth, the US EPA has

these go back into the soil as straw,

identified thousands of properties

and other crop wastes are put back

that could potentially host solar,

on the land.

wind or biomass energy production facilities. EPA used Google Earth to

‘The final stage, food, must be

find the sites.

Mr Andrei Savinykh, deputy

removed from the production

permanent representative at his

chain,’ he said, ‘and we must

EPA worked with the Department of

country’s mission to the UN in

substitute instead an agro-

Energy’s National Renewable

Geneva, Switzerland, told delegates

industrial product in the form of

Energy Laboratory to collect

at the conference that his

biofuels. In addition, we must add

information on renewable-energy

government was convinced by

safe processing and storage of

availability across the country, and

scientific advice that repeated

radionuclides from the final waste.

merged it with EPA’s data from

harvesting of biomass crops as

Then we can expect that repeated

several land clean-up programmes.

feedstock for biofuel refineries

harvesting of biomass crops which

In addition, EPA applied screening

would remove radionuclides from

absorb the radioactivity will remove

criteria, including distance from

the soil in the contaminated areas.

it once and for all. Instead of

power lines, closeness to roads, and

414

Clean-up & regeneration bulletin

site acreage, to identify sites that are

missed qualifying for Superfund

Greenstone is now investigating

good candidates for hosting

remediation. Greenstone’s

whether there are health benefits

renewable-energy production

hypothesis was that people living

from these clean-ups.

facilities.

nearby value the clean-ups. He tested whether neighbourhoods

The properties offer a number of

‘We are facing a wide range of

adjacent to Superfund sites became

attractive features for the

environmental problems, including

more desirable after clean-ups.

the severe threats to our well-being

development of renewable-energy facilities, including: • appropriate location, useful infrastructure such as transmission lines and roads, and appropriate zoning for development; • landowners and local communities that are often eager to see new economic uses for these properties; • an alternative to using green spaces, which may help reduce community concerns about the effects of a planned renewableenergy facility.

posed by climate change and water Superfund, a federal government

and air pollution,’ Greenstone said.

programme that cleans up the

‘The findings suggest that less

largest and most dangerous

ambitious clean-ups like the

hazardous waste sites in the US, was

erection of fences, posting of

signed into law in 1980. Almost

warning signs around the sites, and

1600 sites have been identified and

simple containment of toxics would

made eligible for federally led clean-

free up resources to address

ups. Clean-up activities have been

environmental problems that have a

concluded at approximately two-

higher payoff.’

thirds of these sites. The average

Source: MIT News Office

cost of a completed clean-up is estimated at more than $55m. The remaining sites is an additional

‘Super worms’ evolving in contaminated land

$30bn.

Research by Dr Mark Hodson of the

expected cost to clean up the

University of Reading, into how Information about renewable-

Greenstone finds that the clean-ups

earthworms can help scientists

failed to cause increases in house

understand more about

prices or rental rates. Indeed, the

contaminated soil and its potential

changes in prices and rental rates

impact on house-building on

are equal to the changes in the

brownfield sites, was presented at

neighbourhoods surrounding the

the BA Festival of Science in

Research

hazardous waste sites where clean-

Liverpool.

Clean-ups may not be worth the cost, finds MIT study

ups did not take place. In addition,

energy development potential on contaminated lands: http:// www.epa.gov/ renewableenergyland

In a paper ‘Does hazardous waste matter? Evidence from the housing market and the Superfund

the populations of the

The research examines why some

neighbourhoods and rate of new

populations of earthworms can

home construction remained at

inhabit contaminated soil and what

their pre-clean-up levels.

impact earthworms have on potentially toxic elements in soils.

program,’ published in the August issue of the Quarterly Journal of

The paper also finds that the

Economics, Michael Greenstone,

average clean-up takes 12–13 years

the 3M Professor of Environmental

to complete and costs around $55m.

Economics at MIT and a colleague,

‘The lengthy interventions are

Justin Gallagher, compared

disruptive and very expensive,’ said

housing markets surrounding

Greenstone. ‘The housing market’s

hazardous waste sites chosen for

clear message is that the clean-ups

Superfund clean-ups to those

are not worth it to the people living

surrounding sites that narrowly

near these sites.’

415

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

A combination of laboratory, field

several papers relating to

‘But it is even more surprising to

and synchrotron X-ray experiments

contamination of soil and

find an increasing number of

have led to the finding that metal-

groundwater.

microbes that can digest hydrocarbons without needing

tolerant populations of super earthworms are evolving. Modern X-ray absorption spectroscopy techniques, such as EXAFS (Extended X-ray Absorption Fine Structure) and XANES (X-ray Absorption Near Edge Structure), are allowing researchers to examine the earthworms, the soil and the burrows as never before. Dr Hodson said: ‘As a surgeon can examine your vital organs to gain an understanding of how your body is functioning, we can now look inside an earthworm and see what is happening to the metals that have been ingested along with the soil. The size of the metal samples we are tracking is around one thousand times smaller than a grain of salt, so invisible to the human eye and impossible to detect in this level of detail with our standard laboratory microscopes. ‘Earthworms are the biggest beasts in the soil, and the best way to establish if the soil is healthy is to ask the animals that live there. If, with the help of modern synchrotron science, we can learn enough about what the earthworms are capable of doing to the soil, they could also become 21st century ecowarriors by helping to tackle soil pollution more efficiently than man

oxygen.’

Oil-eating microbes give clue to ancient energy source

‘The striking diversity of micro-

Microbes that break down oil and

organisms that can break down

petroleum are more diverse than

hydrocarbons may reflect the early

previously thought, suggesting

appearance of these compounds as

hydrocarbons were used as an

nutrients for microbes in Earth’s

energy source early in the Earth’s

history; bacteria and archaea living

history, according to Dr Friedrich

with hydrocarbons therefore may

Widdel from the Max Planck

have appeared early in the evolution

Institute for Marine Microbiology in

of life,’ said Dr Widdel.

Bremen, Germany. These microbes can change the composition of oil

These bacteria and archaea thrive in

and natural gas, and can even

the hidden underworld of mud and

control the release of some

sediments. You can find them in

greenhouse gases. Understanding

sunken patches of oil under the sea;

the role of microbes in consuming

in oil and gas seeping out

hydrocarbons may therefore help us

underground; and maybe even in oil

access their role in the natural

reservoirs. Their product, hydrogen

control of climate change.

sulphide, may nourish an unusual world of simple animal life around

‘Hydrocarbons like oil and natural

such seeps, via special symbiotic

gas are made up of carbon and

bacteria.

hydrogen; they are among the most abundant substances on Earth,’ said

Scientists have identified particular

Dr Widdel. ‘Even though we use

symbioses between archaea and

them as fuel sources, they are

bacteria that are capable of

actually very unreactive at room

consuming the greenhouse gas

temperature. This makes them

methane before it can escape from

difficult to use as a biological energy

the ocean’s sediments. Others that

source, particularly if there is no

have been discovered contribute to

oxygen around.’

the bioremediation or cleaning up of petroleum-contaminated water

For over 100 years, scientists have

supplies in underground aquifers.

known that microbes such as bacteria can use hydrocarbons like

‘This astounding oxygen-

oil and gas as nutrients. But this

independent digestion of

process usually requires supplies of

hydrocarbons is only possible via

oxygen for it to work at room

unique, formerly unknown

temperature. ‘Scientists were

enzymes,’ said Dr Widdel. ‘By

The Society for General

always fascinated by the microbes

getting a better understanding of

Microbiology’s Autumn meeting in

that do this, because hydrocarbons

the way these enzymes and

Dublin in September 2008 featured

are so unreactive,’ said Dr Widdel.

microbes are functioning we will

has been able to up until this point in history.’ Source: University of Reading

416

Clean-up & regeneration bulletin

also have a better understanding of

area of land well away from water

compounds in the sheep-dip tank

natural greenhouse-gas control and

courses. This allows specialized

under laboratory conditions.

the way hydrocarbons are naturally

bacteria in the soil to degrade the

recycled into carbon dioxide.’

sheep-dip over the next couple of

Source: Society for General

months, hopefully before it can get

Microbiology

into rivers or streams.’

degraded 75% of the compound,

Bacteria stop sheep-dip from poisoning fish and bees

However, in rural economies in

Cannon. ‘We think these bacteria

Ireland, where agriculture provides

could be added into sheep-dip tanks

over 10% of employment and

to break down the insecticides prior

economic turnover, and in upland

to land disposal. We know they can

Wales or Devon where sheep are a

survive because they originally

major farming activity and sheep-

came from inside a sheep-dip tank.’

Bacteria can be used to break down used sheep-dip, preventing bees and fish from dying because of soil and river contamination, according to Dr Mairin Cannon of University College Dublin. Most modern sheep-dips are based on natural insecticides found in

dips are routinely used to control parasites, heavy rainfall can cause used sheep-dip to leach out into waterways and sediments, where it can kill huge quantities of fish.

‘One type of bacterium originally taken from a sheep-dip tank, which is unprecedented,’ said Dr

‘It is vital that we do our utmost to prevent fish kills in the future,’ said Dr Cannon. ‘Most recently there have been several reports of fish kills as a result of sheep-dip

Synthetic pyrethroids are also

pollution in the UK. The best way to

extremely toxic to aquatic

degrade synthetic pyrethroids in an

invertebrates such as leeches, water

environmentally friendly manner is

snails and beetles and are

to use these naturally occurring

particularly toxic to bees, which can

bacteria before the dip gets out into

lead to problems with pollination.

the environment. This could

Once the poison is absorbed by

prevent a cascade of detrimental

these animals, it can move up the

effects to fish, bees, aquatic

food chain, accumulating as it goes.

invertebrates and ultimately

insects.

‘In order to prevent pollution of this

humans.’

kind, we looked at bacteria taken

Source: Society for General

‘Synthetic pyrethroid compounds

from sheep-dip-contaminated soils

Microbiology

are far less toxic to humans than

in the hope that they could degrade

other insecticides, such as the

the pyrethroids in the sheep-dip

organophosphates formerly used

before it is spread on land,’ said Dr

for removing disease-causing

Cannon.

chrysanthemum flowers. These have been manufactured synthetically since the 1970s, and are known as pyrethroids. These pyrethroids are commonly used in household products like head-lice shampoo, ant powders and fly sprays, as well as agricultural products designed to control

Colour-coded bacteria spot oil spills, leaky pipes and storage tanks Oil spills and other environmental

insects from sheep, but they are actually a thousand times more

Thirty different bacteria were

pollution, including low-level leaks

toxic to fish,’ said Dr Cannon. ‘They

isolated from sheep-dip-polluted

from underground pipes and

may also cause cancer in people,

soil and dipping tanks. Previously,

storage tanks, could be quickly and

according to the US Environmental

similar bacteria had been found to

easily spotted in the future using

Protection Agency.’

degrade synthetic pyrethroids at

colour-coded bacteria, according to

low concentrations. Dr Cannon

Professor Jan Van der Meer of the

‘Just one cupful of used sheep-dip

tested the bacteria to see if they

University of Lausanne,

could wipe out all the fish in an

could degrade the pyrethroids at

Switzerland.

entire river,’ said Dr Cannon. ‘The

higher concentrations – before the

current advice is to dilute sheep-dip

sheep-dip was diluted. They found

‘Because bacteria have simple

with two parts of water to one part

eight different bacteria that could

single-celled bodies, it is relatively

dip, then spread it on a designated

break down the pyrethroid

easy to equip them with a sensor

417

Land Contamination & Reclamation / Volume 16 / Number 4 / 2008

and a brightly coloured “reporter

Van der Meer. ‘The environmental

to surfaces like rocks – or seabirds

protein” which shows up under a

benefits of this research are very

and shellfish – where they can last

microscope, alerting us to different

clear. Our methods and results

for many years, making it tricky to

substances leaking into the soil or

show how relatively simple and

detect small leaks or ancient sources

seawater from oil spills, agricultural

cheap assays could be used as a first

of pollution.

chemicals or other pollutants,’ says

line of defence to judge

Professor Jan Van der Meer.

contamination in the environment.

‘The bacteria can detect different

Once positive values are obtained,

mass transfer rates of the