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Mercury Methylation, Demethylation, and Bioavailability in the Hyporheic Sediments of a Northern Wisconsin Wetland

It is generally accepted that wetland sediments have a high   potential to produce methylmercury, yet the factors controlling the   relevant chemical transformations are poorly understood. Previous   studies suggest that sulfate-reducing bacteria play an important   role in methylation, but iron-reducing bacteria may also participate   in this process. Methylation rates are influenced by both the   concentration of Hg(II) and its speciation, which affects its   bioavailability. Net accumulation depends also on demethylation   rates, rates which may be significant in these systems. The   objective of this study is to gain a better understanding of the   main factors controlling the bioavailability of inorganic mercury   for the production of methylmercury in wetland hyporheic zones.    Stable isotopes of mercury are being used to investigate potential   methylation and demethylation rates in the hyporheic sediments of   Allequash Creek, near Boulder Junction, WI. Other techniques that   are being applied to examine the chemical and biological drivers of   mercury methylation and bioavailability include tin-reducible   mercury "titrations" to measure the concentration of strong mercury-  binding ligands in porewater, 14C-acetate uptake assays to determine   the activity of the native microbial consortia, ion exchange resin   experiments to explore the role of dissolved organic carbon in   mercury binding, and inhibition studies (e.g. sodium molybdate   amendments) of sulfate-reducing bacteria to assess their role in   producing methylmercury. Manipulations of environmental conditions   in laboratory microcosms are being used to determine the relative   importance of physical factors, such as temperature, and   biogeochemical factors, such as sulfate, sulfide, dissolved organic   carbon (DOC), and iron levels, on the fate of mercury in hyporheic   systems.     (mercury); (methylmercury); (wetland); (wetlands); (anoxia);   (anoxic); (sulfate-reducing bacteria); (toxic metal); (toxic   metals); (chemicals of concern); (chemical of concern);   (demethylation); (Wisconsin)

Status
In progress
Type
Project
Start Date
End Date
Researchers
Joel CreswellPrincipal Investigator
Associated with 2 projects
Agencies
Environmental Protection Agency $ 74,000.00USDEstimates

Funding 21 projects for a total of $7,345,444.00
Scope of Study
Laboratory Investigation
Scale of Phenomena
Biochemical
Physical/Chemical
Impact of Pollutants
Toxic Metals
Land Use and Habitat
Wetlands
State Province
Wisconsin
Annex Numbers
Persistent Toxic Substances
Remedial Action Plans and Lakewide Management Plans
Research & Development
Specific Objectives for toxic substances and effluents
General
Annex
  • Annex Numbers
    Annex Numbers
    Persistent Toxic Substances
    Remedial Action Plans and Lakewide Management Plans
    Research & Development
    Specific Objectives for toxic substances and effluents
  • Annex 17

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