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The impact of VSLH treated water water,” says1:DrSchema c Tegtmeier. This Figure of method naturalleads and anthropogenic Veryfrom Short-Lived Halodepends to a large degree on where the to a significant increase in the production of carbons (VSLH) emissions and their impact on atmospheric processes. water is released and the prevailing transport VSLH, a drawback that is avoided in the second patterns. The ozone layer is located at method of treating water, based on the use of between 20-25 km above the Earth’s surface, UV light. “The UV method will not lead to in the stratosphere, and gases need to get into the production of halocarbons – only the use uplift regimes around the tropics in order to of oxidants like ozone and chlorine will have make it to this kind of altitude. “This is where such an effect,” explains Dr Tegtmeier. Many the short-lived species are very different shipping and industrial companies are likely from the long-lived species, the CFCs,” says to use the chlorination method however, as Dr Tegtmeier. While long-lived species often it’s cheaper than the UV method and allows circulate for long enough in the atmosphere to them to treat huge volumes of water.
VSLH can be easily emitted from the ocean into the atmosphere. My research is about finding out what effects these gases have in the atmosphere once they are released from the treated water. VSLH emissions In her research, Dr Tegtmeier aims to assess the likely extent of future emissions of VSLH, and their wider impact on the atmosphere. “We want to quantify the amount of halocarbons that are going to be produced in industrial and ballast water, if we assume that the majority of companies will use the chlorination method,” she outlines. “VSLH can be easily emitted from the ocean into the atmosphere. My research is about finding out what effects these gases have in the atmosphere once they are released from the treated water.”
eventually reach the tropics, from where they can get into the stratosphere, it’s different for the short-lived species. “After a while they are chemically destroyed, and if they haven’t been taken into the stratosphere by this point, they won’t affect the ozone layer,” explains Dr Tegtmeier. “But if they are emitted in the tropical oceans, the region where the convective uplift regimes are located, they can be transported into the stratosphere.” The location of these uplift regimes holds clear importance to assessing the likely impact of VSLHs on the ozone layer, which is a major priority for Dr Tegtmeier. The
EU Research
Figure 3: Annual mean surface (20 m) spread of disinfection by-products from discharge in Singapore relative to the total number of particles released. Contours show the area of the percentage of particles (30%, 50%, 70% and 90%) characterised by the highest density.
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Above figures from: Maas, J., Tegtmeier, S., Quack, B., Biastoch, A., Durgadoo, J. V., Rühs, S., Gollasch, S., and David, M.: Simulating the spread of disinfection by-products and anthropogenic bromoform emissions from ballast water discharge in Southeast Asia, Ocean Sci., 15, 891-904, https://doi.org/10.5194/os-15-891-2019, 2019.
core question here is the quantity of VSLHs that could reach the stratosphere. “We have to deal with large uncertainties, because we don’t really know how many ships and industrial companies will use chlorination and how many will use the UV method,” outlines Dr Tegtmeier. It is also important to be aware that the amount of VSLH produced in treated water can vary significantly, largely due to environmental conditions, such as the amount of organic material. It is however possible to look at various different scenarios, from which Dr Tegtmeier can then build a more complete picture. “If we assume a worst-case scenario, we find a much larger amount of halocarbons produced by industry than assumed so far,” she continues. “If this does prove to be the case, I think there would need to be some level of communication with the industry.”
Macroalgae farms The growth of macroalgae farms is another major consideration in terms of assessing the likely future level of VSLH in the atmosphere. Macroalgae have very different halocarbon production rates, an issue that Dr Tegtmeier and her colleagues aim to understand in
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A New Threat A New Threat to the Stratospheric Ozone Layer from Anthropogenic Very Short-lived Halocarbons Project Objectives
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Figure 1: Schematic of natural and anthropogenic Very Short-Lived Halocarbons (VSLH) emissions and their impact on atmospheric processes.
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the ozone layer has been a major concern since the problem was brought to wider attention in the 1970s, leading eventually to the Montreal Protocol of 1987, which sets limits on the emissions of chlorofluorocarbons (CFCs). While this has led to the onset of ozone recovery, increased levels of Very Short-Lived Halocarbons (VSLH) might represent a new threat to the ozone layer. “We find VSLH in coastal waters where there are a lot of macroalgae, for example,” says Dr Susann Tegtmeier. While VSLH have long been present in the oceans, forming part of the background state, anthropogenic activities such as oxidative treatment of industrial water and ship ballast water are leading to greater emissions, a topic at the core of Dr Tegtmeier’s research. A ship usually takes on ballast water during cargo unloading in one harbour and discharges the ballast water during loading operations in another harbour. A lot of bacteria and small living organisms in the ballast water can spread more widely in the new eco-systems after being released, potentially causing serious problems. “Some of these marine invasive species have proved to be very damaging. For instance, the Zebra mussel has invaded many parts of the Baltic Sea and is now causing large economic losses for electric power generators by blocking their water intake pipes,” outlines Dr Tegtmeier. In order to address this problem, the International Maritime Organisation (IMO) adopted an agreement on the management and cleaning of ballast water, which came into force in 2017. “We will see an increase in the cleaning of ballast water over the next four or five years,” continues Dr Tegtmeier. The treatment of industrial water represents another major source of halocarbons, and while the concentrations are lower than in ballast water, the overall quantity involved is higher. Nuclear power plants use large volumes of water in cooling, for example, which also needs to be treated before it can be released. In general, there are two different methods of cleaning industrial cooling and ballast water. “One involves adding oxidants, such as chlorine, to the
Qinhuangdao Inchon Dalian Pyeongtaek NagoyaTokyo Qingdao Busan Ulsan Kwangyang 20 Kobe Chiba Kitakyushu 5800 Shanghai Ningbo 250
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Figure 2: Estimated annual ballast water discharge volume from each harbour in the modified world port ranking in Southeast Asia with the names of the largest 26 ports. Contours and black contour lines show climatological ocean surface velocities [cm s-1]
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The ozone layer is thought to be recovering after the production of CFCs was banned in the ‘80s, yet increased emissions of Very-Short Lived Halocarbons (VSLH) from treatment of industrial and ballast water could represent a new threat. We spoke to Dr Susann Tegtmeier about her work in assessing the likely extent of future VSLH emissions and their wider impact on the atmosphere.
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greater depth. “What is the contribution of the macroalgae farms to the total amount of halocarbons coming from all macroalgae?” she outlines. The possibility of developing larger-scale macroalgae farms has attracted attention as a means of capturing and storing carbon; while this is a major global priority, Dr Tegtmeier believes it’s important to first assess the likely impact of these farms. “This is something we want to monitor and understand. Macroalgae farms on the open ocean might have a very big impact on ozone chemistry,” she cautions. This is not an immediate prospect however, and at this stage Dr Tegtmeier is focused more on investigating what happens in the ocean and the atmosphere after ballast or industrial water has been released. This is closely related to the question of how increased levels of VSLH will affect the ozone layer. “What will happen with the ozone layer in the future? What will be the impact of various anthropogenic activities? As scientists, we try to build a deeper understanding of the effects that increased emissions would have,” says Dr Tegtmeier. These questions will form a central part of Dr Tegtmeier’s research agenda over the coming years.
There is only an emerging awareness of the impending increase of atmospheric VSLH, which represents a new threat to ozone recovery. In addition to the damaging effect on the ozone layer, increased levels of VSLH will also impact the radiative forcing and the oxidizing capacity of the atmosphere - the capacity of the atmosphere to ultimately remove many species emitted from natural and anthropogenic sources. Assessing future emissions of anthropogenic VSLH, their multisided impact on atmospheric chemistry and physics, and in particular their potential to prolong stratospheric ozone depletion (Figure 1), is therefore a correspondingly high priority.
Project Funding
The project is supported by the Emmy Noether programme of the German Research Foundation (DFG).
Contact Details
Project Coordinator, Dr Susann Tegtmeier GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel Düsternbrooker Weg 20 24105 Kiel T: +49 (0)431 600-4160 E: stegtmeier@geomar.de W: https://www.geomar.de/index. php?id=stegtmeier
Dr Susann Tegtmeier
Dr Susann Tegtmeier is an Emmy Noether Research Group Leader at the Helmholtz Centre for Ocean Research (GEOMAR) in Kiel, Germany. Previously she held Fellowships at institutions in Germany and Canada. She teaches courses on several different areas of meteorology, oceanography and climate dynamics, and has published 35 peerreviewed papers. She will be starting a faculty position at the University of Saskatchewan in September 2019.
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