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Project Summary Sheet

U.S. Geological Survey, Greater Everglades Science Initiative (Place-Based Studies)

Fiscal Year 2003 Project Summary Report

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

Project Start Date: 10/1/00 Project End Date: 9/30/05

Web Sites:;;;

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

Funding Source: USGS's Greater Everglades Science Initiative (PBS)

Principal Investigator(s): George Aiken,

Project Personnel: Jarrod Gasper,, Kenna Butler,

Supporting Organizations: Florida Department of Environmental Protection, South Florida Water Management District

Associated / Linked Projects: Ones by (Krabbenhoft, Orem, Kendall)

Overview & Objective(s): The objective of this project is to better define the roles of dissolved organic matter (DOM) in controlling the reactivity, bioavailability and transport of Hg in the Everglades. Our goal is to provide fundamental information on the nature and reactivity of DOM in the Everglades. Data and findings 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. The results of this research are critical for the design of effective management strategies for the ecological restoration of the Everglades and for mitigating mercury contamination of game fish in South Florida

Status: The project is presently in the 3rd year of a 5-year effort. Currently we are focusing on 5 major study elements important for future management strategies: 1.) Hg-DOM binding studies designed to define the chemistry of DOM-Hg interactions and to improve geochemical models of the system; 2.) Assessment of the effects of DOM on Hg methylation in field mesocosm studies; 3.) Determination of the impacts of wet/dry cycling of the wetlands on Hg and DOM cycling; 4.) Characterization of the geochemistry of new Storm Treatment Areas (STAs); 5.) Characterization and monitoring of changes in DOM and water quality throughout the Everglades system.

Recent & Planned Products: Overall, this work has resulted in 1 PhD (1999), 2 Masters Theses (2000,2001) and 7 journal articles prior to FY02. In the past year, the following journal articles have been published:

Haitzer, M., Aiken, G.R., Ryan, J.N. 2003 Binding of Mercury to Aquatic Humic Substances, Environmental Science and Technology, vol. 37, 2436-2441.

Drexel, E.T., Haitzer, M., Ryan, J.N., Aiken, G.R., Nagy, K. 2002 Mercury Sorption to two Florida Everglades Peats:Evidence for Strong and Weak Binding and Competition by Dissolved Organic Matter Released from Peat. Environmental Science and Technology, vol. 36, 4058-4064.

Haitzer, M., Aiken, G.R., Ryan, J.N. 2002 Binding of Mercury to Dissolved Organic Matter, Environmental Science and Technology, vol. 36, 3564-3570.

Planned: Masters Thesis (2003); 5 journal articles in preparation.

Relevance to Greater Everglades Restoration Information Needs: The information provided by this project is important for the design of remediation strategies. Vegetation and hydrology, for instance, are important in controlling both DOM and Hg reactivity. In addition, our research efforts to study Hg-DOM interactions and Hg-DOM binding constants are critical for adequate modeling of Hg in the Everglades. Finally, the research is important for drinking water, pollutant transport and ASR issues. This project is relevant for the following items in the USGS Science Plan in Support of Everglades Restoration: Restoration Goal 1A: SO1, SO4; 1B: SO1, SO3, SO4, SO5 and Restoration Goal 3, SG 1, SG 4.

Key Findings:

  1. Strong Hg-DOM constants, critical for geochemical and biochemical models, successfully determined.
  2. DOM exerts strong controls on HgS, a key form of Hg in areas where methylmercury is formed.
  3. Mesocosm experiments demonstrate direct influence of DOM on bioaccumulation of Hg by fish.
  4. Drying/rewetting of Everglades results in increased rates of Hg methylation. Amount and reactivity of DOM strongly dependent on hydrologic conditions and nutrient inputs to the Everglades.

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