The Role of Dissolved Organic Carbon in Aquatic Mercury Cycling

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11/15/2003 - 9/14/2008

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  • James Hurley, UW-Madison
  • Michael Tate, UW-Madison
  • David Krabbenhoft

Although our scientific understanding of mercury sources, cycling and fate in the environment has improved greatly in the past 10 years, we still lack a robust understanding of the role of watersheds in controlling the response time of aquatic ecosystems to changing loads of atmospheric mercury deposition. The subsequent generation of methylmercury (MeHg) — the most toxic and bioaccumulative form of mercury — is also of interest. For the past sixteen years, the USGS Mercury Research Lab and the University of Wisconsin-Madison have partnered on research projects to further the scientific understanding of mercury sources, cycling, fate, and toxicity in the environment. These collaborative efforts have resulted in fundamental scientific discoveries that have transfer value across the globe. In this research, UW-Madison scientists will provide technical assistance and leadership for the Mercury Experiment To Assess Atmospheric Loadings In Canada and the United States (METAALICUS) project, and for the Coastal Zone Atmospheric Mercury Deposition (CZAMD) project. The goal of the METAALICUS collaboration is to determine the relative importance mercury derived from uplands and wetlands on the accumulation of mercury in fish. UW-Madison scientists will examine the role of DOC in the transport and speciation of Hg and MeHg. We will examine the pathways and transport rates of mercury from the uplands to the lake. By using a geochemical and hydrological integrated approach we will examine important processes to determine those driven by physical transport mechanisms (e.g., erosion) versus geochemical transport mechanisms (e.g., co-transport with dissolved and colloidal organic carbon). One goal of CZAMD project is to assess whether the marine boundary layer causes enhanced levels of Hg oxidation and deposition in the near coastal environment; another goal is to understand the processes that control this phenomenon and its spatial and temporal trends. Recent observations of Hg deposition in coastal zones of the USA show enhanced levels of deposition. We will evaluate whether man-related and/or natural factors are the driving force behind the Hg deposition. UW-Madison scientists will provide expertise in monitoring, data management, and interpretation of the results.

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