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Project Summary Sheet

U.S. Geological Survey, Greater Everglades Science Program: Place-Based Studies

Fiscal Year 2002 Project Summary Sheet

Project: Interactions of Mercury with Dissolved Organic Carbon in the Everglades

Web Sites: http://sflwww.er.usgs.gov/exchange/Aiken/methodchem.html; http://sflwww.er.usgs.gov/people/Aiken.html; http://sofia.usgs.gov/sfrsf/rooms/mercury; http://er.usgs.gov/projects/everglades_mercury;

Location (Subregions & Counties): Central Everglades; Palm Beach, Broward and Miami-Dade County

Funding (Source): USGS Place-Based Studies

Principal Investigator(s): George Aiken, graiken@usgs.gov, 303-541-3036

Project Personnel: Jarrod Gasper , jgasper@usgs.gov, 303-541-3050

Supporting Organizations: National Science Foundation

Associated Projects: Ones by Krabbenhoft, Orem, and Kendall

Overview & Status: Interactions of mercury (Hg) with dissolved organic matter (DOM) play important roles in controlling reactivity, bioavailability and transport of Hg in the Florida Everglades. This project is designed to define the nature and magnitude of these interactions. As part of this research, we studied the distribution and nature of DOM in the northern Everglades. We noted the importance of source materials (peat versus vegetation and periphyton), and the importance of hydrologic factors on the quality and amount of DOM in a given location. Differences in the DOM were clearly apparent in regions exhibiting different behavior with regard to the generation of methylmercury. We also studied the reactivity of Everglades DOM with mercury through cinnabar (HgS) dissolution and formation experiments, and a variety of methods designed to yield information on Hg-DOM binding constants. The results of the cinnabar interaction studies have been published as 2 journal articles (Environmental Science and Technology, 1998, Vol. 32, pp. 3305-3311; Environmental Science and Technology, 1999, Vol. 33, pp. 1418-1423), a PhD thesis (1999) and a Masters thesis (2001). Ongoing Hg-DOM binding studies have demonstrated that the strength of Hg-DOM interactions is strongly dependent on the ratio of Hg to DOM, and, under environmentally relevant conditions, DOM interacts more strongly with Hg than indicated by previous studies. Currently, we are working on including the strong DOM-Hg binding components in geochemical models and to assess the effects of DOM on Hg methylation in field mesocosm studies. Finally, we also studied the interactions of DOM with calcite in the Everglades (Geochimica et Cosmochimica Acta, 2000, Vol.64, pp.61-72), and the distribution of Hg between dissolved and particulate phases (Todd Drexel, Masters thesis, 2000, University of Colorado). Presently, 5 journal articles are in different stages of publication.

Needs & Products: Effective management strategies for the ecological restoration of the Everglades and for mitigating mercury contamination of game fish in South Florida requires understanding of factors and processes resulting in the transport and controlling the reactivity and bioaccumulation of Hg in the Everglades. Our project focuses on the effect of DOM on the transport and reactivity of Hg in the Everglades. The data gathered by our project are published primarily in the form of journal articles that contribute to the basic understanding of how the Everglades system functions with regard to the nature and reactivity of DOM, and how the quality of the DOM controls the reactivity of Hg in the Everglades. Results of this research will be used by the U. S. Geological Survey, U.S. EPA, Florida Department of Environmental Protection, and the South Florida Water Management District.

Application to Everglades Restoration: This information is important to consider in designing remediation strategies. Factors such as vegetation and hydrology, for instance, are very important in controlling both DOM and Hg reactivity. In addition, our research efforts to study distribution of Hg between DOM and particulate organic matter, and, the determination of Hg-DOM binding constants are critical for adequate modeling of Hg in the Everglades. Finally, the research is important for understanding drinking water, pollutant transport and ASR issues involving DOM.

Study Milestones
Familiarity xxxx xxxx xxxx     xxxx xxxx        
Design xxxx xxxx xxxx xxxx              
Field Work   xxxx xxxx xxxx xxxx xxxx xxxx xxoo oooo oooo  
Data Analysis   xxxx xxxx xxxx xxxx xxxx xxxx xxoo oooo oooo oooo
Initial Reporting       xxxx xxxx xxxx xxxx xxoo oooo oooo oooo
Quality Assurance       xxxx xxxx xxxx xxxx xxoo oooo oooo oooo
Results Published       xxxx xxxx xxxx xxxx xxoo oooo oooo oooo
Synthesis   xxxx xxxx xxxx xxxx xxxx xxxx xxoo oooo oooo oooo
Note: "x" indicates task completed, and "o" indicates task planned, but not completed

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