State Water Resources Research Institute Program

Project ID: 2007CA191B
Title: Control of Mercury Methylation in Wetlands Through Iron Addition
Project Type: Research
Start Date: 3/01/2007
End Date: 2/28/2008
Congressional District: 43
Focus Categories: Ecology, Wetlands
Keywords: Ecosystems Wetlands
Principal Investigator: Sedlack, David L
Federal Funds: $ 17,352
Non-Federal Matching Funds: $ 51,332
Abstract: Throughout California and other regions of the United States, fish consumption advisories have been established to minimize human exposure to mercury. In many locations, the reproduction of wildlife also is threatened by exposure to mercury. Threats to human health and aquatic ecosystems posed by mercury are related to the tendency of inorganic mercury to be converted into methylmercury, a toxic form of the metal that readily bioaccumulates in aquatic food webs. Available research indicates that much of the methylmecury formation in aquatic ecosystems occurs in wetland sediments. Because vast areas of sediments in California are contaminated with mercury, wetland restoration may exacerbate mercury problems by increasing the loading of methylmercury to aquatic ecosystems.

To reduce the net formation of methlmercury in wetlands without compromising wetland function, we propose to add low levels of iron to wetland sediments. Addition of iron is practical because the doses needed are relatively low and inexpensive forms of iron are readily available from commercial sources. Previous studies in our laboratory have shown that addition of modest amounts of iron to wetland sediments can reduce net methylmercury production by approximately 75%. The proposed research will extend the previous laboratory studies to address the effects on mercury methylation of tidal cycles, aquatic plants and exchange of gases between the sediments and the atmosphere. The experiments will be conducted using sediment cores collected from California wetlands. The proposed research has the potential to provide a practical, inexpensive and effective way to reconcile the competing objectives of wetland habitat restoration and protection of aquatic food webs from the adverse impacts of mercury.

Progress/Completion Report, PDF

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