To meet these objectives, we have adopted a combined field/ laboratory approach. In conjunction with other research projects our field efforts are designed (1) to characterize DOM at a variety of field locations chosen to provide information about the influences of hydrology, seasonal factors (wetting and drying events) and source materials (e.g. vegetation, periphyton, peat) on the nature and amount of DOM in the system, and (2) to elucidate the roles of DOM in controlling the reactivity and bioavailability of Hg in the Everglades.
George Aiken Dave Krabbenhoft, Orem, Bill, 2005, Interactions of Mercury with Dissolved Organic Carbon in the Florida Everglades.Online Links:
FY 2003 - 2004 project personnel include Jarrod Gasper and Kenna Butler. Previous project personnel include Michael Reddy, Paul Schuster, James Weishaar, Jason Tregellas, and Janece Koleis.
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This research is relevant because of the high natural production of organic carbon in the peat soils and wetlands, the relatively high carbon content of shallow ground water systems in the region, the interactions of organic matter with other chemical species, such as trace metals, divalent cations, mercury, and anthropogenic compounds, the accumulation of organic carbon in corals and carbonate precipitates, and the potential changes in the quality and reactivity of dissolved organic carbon (DOC) resulting from land use and water management practices. Proposed attempts to return the Everglades to more natural flow conditions will result in changes to the current transport of organic matter from the Everglades Agricultural Area and the northern conservation areas to Florida Bay. In addition, the presence of dissolved organic matter is important in the production of drinking water, contributes to pollutant transport, and will influence ASR performance. Finally, interactions of mercury (Hg) with organic matter play important roles in controlling the reactivity, bioavailability and transport of Hg in the Everglades.
We also studied the reactivity of Everglades DOM with mercury through cinnabar (HgS) dissolution and formation experiments, and an ion-exchange technique designed to yield information on Hg-DOM binding constants.
We continued ongoing lab studies to better define interactions of Hg with Dissolved Organic Matter (DOM). These included:
1. Binding studies (Hg-DOM). Ion-exchange studies designed to measure the strength of interactions between Hg and DOC were continued, and, new techniques to assess factors controlling reactivity of DOM with Hg and the strength of binding interactions were investigated. This work is important for accurate modeling of these interactions.
2. Study of the interactions of the DOM with HgS. Experiments were designed to provide insight into ability of DOM to stabilize colloidal HgS. This is a potentially significant process effecting the bioavailability of Hg.
3. The study of the "partitioning" of Hg between dissolved and particulate phases was completed. Field based partitioning coefficients, necessary for accurately modeling Hg behavior in the Everglades, were corroborated.
1. Continue work using field based mesocosms to address issues concerning partitioning and reactivity of Hg in the Everglades with regard to the roles played by DOM in the system. We plan to continue overall project support with regard to DOM analyses and isolate availability for experimentation.
2. Laboratory development of abiotic methods for assessing bioavailability of Hg will be completed, and we anticipate using these techniques in the field.
3. Lab based studies on DOM-Hg binding constants will likely be completed in FY 2002. This includes studies with cinnabar and ion exchange and dialysis techniques for estimating binding constants with Hg. Concerning the latter techniques, we plan to employ these methods to assess interactions between CH3Hg+and OM in the system. These interactions could prove to be important controls on bioavailability of CH3Hg+ in the system.
4. In lab based studies to be carried out in conjunction with Bill Orem, we plan to investigate the interactions of OM and inorganic S in the Everglades. This work will attempt to investigate the role of sulfate anion interactions with both DOM and particulate organic matter (POM). The organic-S in the DOM and the peat are of interest both in regard to binding of Hg and as a potential source of sulfate during oxidation and remineralization of organic matter. We have strong evidence from Phase 1 studies that remineralization can provide significant contributions of sulfate to the porewaters.
Interactions of DOM with Hg in the Everglades
1. Continue lab-based studies on DOM-Hg binding constants. We have recently completed development of dialysis technique for measuring binding constants. This method is the only reliable method we have found for measuring binding constants. Development was carried out using hydrophobic sample from F1 field site. The method now needs to be used with other fractions of the DOM from F1 and other locations in the Everglades and the method should be extended for measuring DOM-MeHg binding constants.
2. Continue lab-based studies on the interactions of DOM with HgS. HgS is assumed to be an important species controlling Hg bioreactivity. Greater definition of DOM-HgS interactions is critical for understanding factors that control methylation of Hg. We previously demonstrated the strong influence of DOM on the chemistry of HgS complexes, although the processes are poorly defined. Efforts in FY 03 and FY 04 will provide data to better understand these processes and assess the role they play in controlling Hg bioavailability.
Effects of DOM on Hg cycling in the Florida Everglades
1. Continue work using field based mesocosms to address issues concerning partitioning and reactivity Hg in the Everglades with regard to the roles played by DOM in the system. Mesocosm experiments have been very successful demonstrating the influence of DOM on methylation and bioaccumulation of Hg. In this work organic matter isolated from areas with reactive DOM is added to mesocosms, in addition to other constituents (sulfate, Hg) to assess impacts on Hg partitioning, methylation and bioaccumulation.
2. Continue work assessing the roles of drying and wetting of peat soils on the generation of DOM and MeHg. Research is both lab and field based. DOM concentrations and changes in the reactivity of the DOM are determined as a function of wetting and drying, a common natural condition and one of great importance in managed wetlands, such as the Storm Treatment Areas (STA). DOM characterization methods established by USGS labs are used.
3. Begin study of DOM in Lake Okeechobee and Kissimmee River. This work is important for future efforts involving ASR. DOM sampling and characterization methods have been established by USGS labs.
4. Begin study of DOM in new Storm Treatment Areas ( STA’s). The STAs are critical for restoration efforts. DOM characterization methods established by USGS labs will be used.
5. Continue assessment of water quality changes in Everglades by participation in ACME Site Survey work. This is done in conjunction with Krabenhoft and Orem. This project is responsible for DOM measurements and characterization throughout the Everglades.
Person who carried out this activity:
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graiken@usgs.gov
Haitzer, M. Aiken, G. R., Ryan, J. N., 2002, Binding of Mercury (II) to Dissolved Organic Matter: The Role of the Mercury-to-DOM Concentration Ration: Environmental Science and Technology v. 36, American Chemical Society, Washington, DC.Online Links:
Benoit, J. M. Mason, R. P., Gilmour, C. C, 2001, Constants for Mercury Binding by Dissolved Organic Matter Isolates form the Florida Everglades: Geochimica Et Cosmochimica Acta v. 65 no. 24, Geochemical Society (Elsevier Science, Ltd.), Oxford, United Kingdom.Online Links:
Ravichandran, M Aiken, G. R., Ryan, J. N., Redd, 1998, Enhanced Dissolution of Cinnabar (Mercuric Sulfide) by Dissolved Organic Matter Isolated from the Florida Everglades: Environmental Science and Technology v. 32, American Chemical Society, Washington, DC.Online Links:
Reddy, M. M. Aiken, G. R., 2001, Fulvic acid-sulfide ion competition for mercury ion binding in the Florida Everglades: Water, Air and Soil Pollution v. 132, Kluwer Academic Publishers, Dordrecht, Netherlands.Online Links:
Drexel, R. Todd Haitzer, Markus, Ryan, Jo, 2002, Mercury (II) Sorption to Two Florida Everglades Peats: Evidence for Strong and Weak Binding and Competition by Dissolved Organic Matter Released from the Peat: Environmental Science and Technology v. 36 no.19, American Chemical Society, Washington, DC.
Reddy, Michael M. Aiken, George R., Schuster,, 1995, Summary of Data from Onsite and Laboratory Analyses of Surface Water and Marsh Porewater from South Florida Water Management District Conservation Areas, the Everglades, South Florida: U.S. Geological Survey, Reston, VA.Online Links:
Bates, A. L. Orem, W. H., Harvey, J.. W., 2001, Geochemistry of Sulfur in the Florida Everglades: 1994 through 1999: USGS Open-File Report OFR 01-007, U.S. Geological Survey, Tallahassee, FL.Online Links:
Orem, William H. Lerch, Harry E., Rawlik, Pe, 1997, Geochemistry of Surface and Pore Water at USGS Coring Sites in Wetlands of South Florida: 1994 and 1995: USGS Open-File Report OFR 97-454, U.S. Geological Survey, St. Petersburg, FL.Online Links:
Bates, Anne L Orem, William H., Harvey. Ju, 2002, Tracing sources of sulfur in the Florida Everglades: Journal of Environmental Quality v. 31 no. 1, American Society of Agronomy, Madison, WI.Online Links:
Hoch, A. R. Reddy, M. M., Aiken, G. R., 2000, Calcite Crystal Growth Inhibition by Humic Substances with Emphasis on Hydrophobic Acids from the Florida Everglades: Geochimica et Cosmochimica Acta v. 64, Elsevier Science Ltd., New York, NY.
Krabbenhoft, D. P. Hurley, J. P., Aiken, G. R., 2000, Mercury Cycling in the Florida Everglades: A Mechanistic Field Study: Verh. Internat. Verein. Limnol. v. 27, E. Scheizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.
Ravichandran, M. Aiken, G. R., Ryan, J. N., Redd, 1999, Inhibition of precipitation and aggregation of Metacinnabar (mercuric sulfide) by dissolved organic matter isolated from the Florida Everglades: Environmental Science and Technology v. 33, n. 9, American Chemical Society, Washington, DC.Online Links:
Haitzer, Markus Aiken, George R., Ryan, Joseph , 2003, Binding of Mercury (II) to Aquatic Humic Substances: Influence of pH and Source of Humic Substances: Environmental Science and Technology v. 37, n. 11, Americal Chemical Society, Washington, DC.Online Links:
Bock, W. D., 1971, A handbook of the benthonic foraminifera of Florida Bay and adjacent waters: Memoir 1, Miami Geological Society, Miami, FL.
Poag, C. W., 1981, Ecological Atlas of Benthic Foraminifers of the Gulf of Mexico: Hutchinson and Ross, Stroudsburg, PA.
Wardlaw, Bruce, editor, 2001, Paleoecological Studies of South Florida: Bulletins of American Paleontology 361, Paleontological Research Institution, Ithica, NY.
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Everglades water chemistry - cations and anions
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Everglades DOC data
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| Data format: | ASCII file of the complete lists of Global Positioning System points reformatted for input into an ARC/INFO point cover in format ASCII |
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Everglades water quality - field parameters
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| Data format: | The file contains a comma-delimited complete list of Global Positioning System (GPS) points in format ASCII |
|---|---|
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<http://sofia.usgs.gov/exchanget/graiken/table5b.csv> |
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Everglades water quality - site & sample information
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Surface Water DOC, Pore Water DOC, and Specific ultraviolet absorbance (SUVA) data
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