paul schuster and mahalingam ravichandran

"Tonight on Mutual of Omaha's Wild Kingdom: 'Mercury Sampling and Alligator Wrestling in the Florida Everglades' with your hosts, Paul Schuster (standing), a research scientist with the U.S. Geological Survey, and Mahalingam Ravichandran (seated), a PhD student at the University of Colorado."

Overview

Over the past decade, high concentrations of mercury contamination have appeared in higher organisms in the聽Florida Everglades. In some locations ("hot spots"), game fish contain mercury levels that require warnings to the public about the hazards of mercury contamination. The waters at these hot spots contain higher levels of methylmercury (CH3Hg+), the species of mercury that accumulates in organisms. Methylmercury is produced by methylation of the mercuric ion (Hg2+) by sulfate-reducing bacteria. Strong complexation of the mercuric ion limits the rate of mercury methylation and uptake by organisms. Our research focuses on the ability of natural organic matter to strongly bind mercuric ions. We've been studying the interactions of natural organic matter from the Everglades and other locations with mercury in aqueous solutions and in sulfide minerals (HgS; cinnabar).聽

This work was initiated by George Aiken and Michael Reddy at the (USGS) laboratory in Boulder, Colorado, as part of the聽聽(ACME) project and the聽.聽 Drs. Aiken and Reddy recruited Mahalingam Ravichandran to work on their project.聽 The NSF Environmental Geochemistry and Biogeochemistry grant received by Joe Ryan, George Aiken, and Kathy Nagy of the Department of Geological Sciences at the University of Colorado follows up on ideas initiated by the USGS work.

ravichandran collecting surface water samples

Mahalingam Ravichandran collects surface water samples from the 2BS site in Water Conservation Area 2B in the Everglades.

Projects

  • The Role of Organic Matter in the Fate of Mercury in the Florida Everglades
    PI: Joe Ryan
    /U.S. Geological Survey/U.S. Environmental Protectional Agency, 1995 to 1998.
  • Interactions of Mercury with Organic Matter in Water and Soil
    PIs: Joe Ryan, George Aiken (USGS), and Kathy Nagy (Geological Sciences, University of Colorado)
    ,听聽(EAR-9807735), September 1998 to August 2001.

Collaborators

  • , U.S. Geological Survey, Boulder, Colorado
  • Prof. Kathy Nagy,听Department of Geological Sciences, University of Colorado, Boulder
  • , U.S. Geological Survey, Boulder, Colorado
  • Appathurai Vairavamurthy,听, Brookhaven, New York

an alligator

Mahalingam Ravichandran collects surface water samples from the 2BS site in Water Conservation Area 2B in the Everglades.

Students and Theses

  • Mahalingam Ravichandran, Ph.D., 1999, Interactions between Mercury and Dissolved Organic Matter in the Florida Everglades. "Ravi" tested the hypothesis that dissolved organic matter from the Everglades could compete with sulfide for the mercuric ion by testing the effect of organic matter on the dissolution and precipitation of cinnabar (HgS).聽 The organic matter, which XANES (x-ray absorption near-edge spectroscopy) analysis showed to contain significant amounts of reduced sulfur moieties, enhanced dissolution following adsorption to the cinnabar surface (Ravichandran et al., 1998).聽 Cinnabar precipitation was prevented if the amount of mercury was less than the amount of reduced sulfur (Ravichandran et al., 1999).
  • Todd Drexel, M.S., 2000, Mercury(II) Sorption to Two Florida Everglades Peats: Effects of pH, Ionic Strength, Calcium, Chloride, and Dissolved Organic Matter. Todd worked under the supervision of George Aiken and Joe Ryan on the binding of the mercuric ion by two peats from the Everglades.聽 Todd's work showed that strong and weak binding sites, thought to correspond with reduced sulfur and carboxyl/phenol functional groups, must be considered to describe mercury binding by the peat.
  • Jake Waples, M.S., in progress. Jake is working under the supervision of Kathy Nagy on the mechanism of organic matter enhancement of cinnabar dissolution.
  • Jarrod Gasper, M.S., in progress. Jarrod is working under the supervision of George Aiken and Joe Ryan on the binding of the mercuric and methylmercury ions by natural organic matter using ion exchange, liquid-liquid extraction, and dialysis techniques.

鈥婸耻产濒颈肠补迟颈辞苍蝉

(with links to PDF files; some PDF files are large -聽2-4 MBytes)聽

a map displaying study sites

Locations of study sites in the Florida Everglades. Sites F1 and 2BS (not shown, about 5 miles south of site U2) were studied in our work.

Presentations

  • Waples J.S., Nagy K.L., Aiken G.R., and Ryan J.N., Dissolution kinetics of cinnabar in the presence of dissolved organic matter. To be presented at the 11th V.M. Goldschmidt Conference, Hot Springs, Virginia, May 2001.
  • Aiken G., Reddy M., Ravichandran M., Ryan J.N., Interactions between dissolved organic matter and mercury. To be presented at the 221st National Meeting of the American Chemical Society, Environmental Chemistry Division, April 2001.
  • Drexel R.T., Aiken G.R., Nagy K.L., and Ryan J.N., Binding of mercury(II) by two peats from the Florida Everglades, 2000. Presented at the International Workshop on Surface Chemical Processes in Natural Environments, Monte Verita, Ascona, Switzerland, October 2000.
  • Drexel R.T., Aiken G.R., Nagy K.L., and Ryan J.N., Mercury(II) sorption to two Florida Everglades peats. Abstracts of Papers of the American Chemical Society, 2000. Presented at the 220th National Meeting of the American Chemical Society, Environmental Chemistry Division, Washington, DC, August 2000.
  • Ravichandran M., Aiken G.R., Ryan J.N., and Reddy M.M., 1999. Inhibition of precipitation and aggregation of metacinnabar (HgS) by humic substances isolated from the Florida Everglades. Abstracts of Papers of the American Chemical Society 217, U746, Part 1. Presented at the 217th National Meeting of the American Chemical Society, Environmental Chemistry Division, March 1999.
  • Ravichandran M., Aiken G.R., Reddy M.M., and Ryan J.N., 1998. Enhanced dissolution of cinnabar (mercuric sulfide) by aquatic humic substances. Abstracts of Papers of the American Chemical Society 216, U785, Part 1. Presented at the 216th National Meeting of the American Chemical Society, Environmental Chemistry Division, August 1998.
  • Aiken G.R., Ravichandran M., Reddy M.M., and Ryan J.N., 1998. Interactions of dissolved organic carbon with mercury in the Everglades, Florida. Abstracts of Papers of the American Chemical Society 216, U765, Part 1. Presented at the 216th National Meeting of the American Chemical Society, Environmental Chemistry Division, August 1998.
  • Ravichandran M., Aiken G.R., Reddy M.M., and Ryan J.N., 1998.聽Enhanced dissolution of cinnabar (mercuric sulfide) by Florida Everglades organic matter. Eos, Transactions of the American Geophysical Union 89, S94. Presented at the Spring Meeting of the American Geophysical Union, May 1998.