Heavy Metals Fractionation and Acid Volatile Sulfide (AVS) in the Bardawil Lagoon Sediments, Norther

Page 1

Development in Analytical Chemistry Volume 2, 2015 doi: 10.14355/dac.2015.02.001

www.seipub.org/dac

Heavy Metals Fractionation and Acid Volatile Sulfide (AVS) in the Bardawil Lagoon Sediments, Northern Sinai, Egypt Mohamed A. Okbah∗1, Alaa M. Younis2 and Gehan M. El Zokm1 Marine Chemistry, National Institute of Oceanography and Fisheries, Alexandria, Egypt

1

Department of Aquatic Environment, Faculty of Fish Resources, Suez University, Suez, Egypt

2

∗1

m_okbah@yahoo.com; 2ala_den@yahoo.com; 1gehanelzokm@yahoo.com

Abstract Bardawil Lagoon in North Sinai, Egypt, is a unique Mediterranean semi-enclosed coastal water body that is listed among the Ramsar Wetlands of International Importance. The present study is to characterize the distribution of some heavy metals (Fe, Cu Pb and Cd) in Bardawil Lagoon sediments and evaluate the sediment quality based on heavy metals fractionation as well as acid volatile sulfide (AVS) and simultaneously extracted metals (SEM). Grain size analysis, carbonate (CaCO3) and organic matter content have been determined in surface sediments collected at 10 stations from the Bardawil lagoon. The results showed high percentage of CaCO3, ranged from 53.5 to 70.5%. The ratio of ∑SEM / AVS was higher than one in Bardwell lagoon sediments (∑SEM / AVS ranged from 1.28 to 9.19). These data would allow us to classify the sediments as toxic. The extractable concentrations of Fe, Cu, Pb and Cd were evaluated in the sediments using sequential extraction procedure. Metals concentration in the exchangeable and carbonate fractions was found in the following order: Fe > Pb > Cu > Cd, whereas they follow the order of Fe > Cu > Pb > Cd in the oxide fraction. In the organic form, metals had the sequence of Fe > Pb ≈ Cu >Cd. The sequences of metals concentration in the residual fraction were as follow: Fe > Pb > Cu > Cd The results of Pb and Cd fractionation reflect the dangers of these metals which more than 75% are associated with the non-residual fractions. Keywords Acid Volatile Sulfide; Bardawil Lagoon; Heavy Metals

Introduction Bardawil Lagoon in North Sinai is one of the most important wetland sites in Egypt. It has been clearly demonstrated that large numbers of migratory birds pass through the area in both spring and autumn; it is an important site for wintering water birds (Dunnet and Crick, 1986). The study of heavy metal concentration in different forms in surface lagoon sediment is an important component in understanding the effect of anthropogenic influences on the aquatic environment. The distribution of metals within the aquatic environment is governed by complex processes of material exchange affected by various natural and anthropogenic activities (Ip et al.2007, Raju, et al. 2011). Heavy metals distribution in Bardawil lagoon sediments showed a common feature of increasing levels of Cu, Pb, and Cd in the western part of the lagoon while high levels of Fe, Zn and Mn in the eastern part (Lofty, 2003). In the bottom sediments of Bardawil lagoon high levels concentration were recorded during the hot seasons (Abdo, 2005), the metals can be introduced to coastal and marine environments through a variety of sources, including industries, wastewaters and domestic effluents (Fu and Wang, 2011). Acid volatile sulfide (AVS) is an operationally defined reactive sulfide fraction that mainly comprises dissolved H2S and mackinawite (FeS), which is considered important for heavy metal fate in reduced sediments (Morse and Rickard, 2004). Heavy metals precipitation with sulfides in reduced sedimentary environments has received considerable attention (DiToro et al., 1992). Sulfides are formed by microbial reduction of SO2_4 when degradation of organic matter takes place under reduced conditions, after O2, NO-3 and Mn- and Fe (II) oxides are depleted (Stumm and Morgan, 1981). Acid volatile sulfide (AVS) has been used to predict the toxicity in sediments of divalent metals, including copper (Cu), cadmium (Cd), nickel (Ni), lead (Pb) and zinc (Zn) (Di Toro et al. 1992; Ankley et al. 1996; Berry et al. 1996). The SEM-AVS concept was developed to predict situations in which toxicity should not occur. Metals in sediment will not be toxic if the molar concentration of AVS is higher than that of SEM

1


Turn static files into dynamic content formats.

Create a flipbook
Issuu converts static files into: digital portfolios, online yearbooks, online catalogs, digital photo albums and more. Sign up and create your flipbook.
Heavy Metals Fractionation and Acid Volatile Sulfide (AVS) in the Bardawil Lagoon Sediments, Norther by Shirley Wang - Issuu