An Assessment of the Impact of Metal-Contaminated Dredge Spoils in Wetland Restoration
Putting tons of dredged sediments to use in restoring degraded wetland habitats helps to solve two problems at once; unfortunately these sediments may contain contaminants whose fate we know relatively little about. The concern is that in chemically complex tidal wetlands dynamic shifts in oxygen availability, redox state and hydration occurring over space and time could mobilize toxic metals contained within the deposited sediments. These shifting dynamics have important implications for living organisms in restored marshes. To better understand these dynamics, Cynthia Gilmour and her colleagues are studying a restored tidal freshwater wetland adjacent to the Anacostia River in Washington, D.C. Their efforts are targeted at understanding the distribution, flux and fate of toxic metals (copper, lead, cadmium, mercury and arsenic) as they undergo various chemical transformations; they are especially interested in anaerobic dredge spoils that are exposed to oxygenated, biologically active conditions in the marsh environment. This study will provide a basic understanding of the release and bioaccumulation of potentially toxic metals in critical wetland habitats and will offer new insights into the use of dredged material for wetland restoration.
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Cynthia C. Gilmour and Gerhardt Riedel
The Academy of Natural Sciences Estuarine Research Center
David Velinsky
The Academy of Natural Sciences
Patrick Center for Environmental Research
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