projects > interactions of mercury with dissolved organic carbon in the florida everglades > 1999 proposal
Project Proposal for 1999
Project number: 4386-34900
Project Title: Interactions of Hg and DOC in the Everglades
Project chief(s): George Aiken, Mike Reddy
Program element(s)/task(s): Element 4/ Task 4.4
Project objectives and strategy: Interactions of Hg with DOC appear to be important in controlling the transport and fate of Hg in the water column. To understand the chemistry of Hg in aquatic systems, better definition of geochemical processes as they apply to DOC is required. Our research will meet this need by focusing on the interactions of the cationic forms of Hg with DOC in a combined field/laboratory study. The characterization of Hg binding resulting from this study will help quantify DOC facilitated transport of Hg in the Everglades. The specific objectives of this research are:
1. To determine the nature and amount of DOC in the Florida Everglades. This work will lead to a more detailed understanding of thc influences of hydrologic and seasonal factors on the nature and the reactivity of DOC at the field study locations.
Potential Impacts and Major Products: Effective management strategies 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. Results of our research will be used by US Geological Survey, South Florida INATURES scientists, US EPA, Florida DEP, and SFWMD. It is expected that the information provided by this project will be used by management agencies in South Florida to implement remediation strategies. The major products of this research will be water quality data published ~ in the form of a USGS Open-file report, journal articles, and a Ph.D. thesis.Collaborators, Clients:
FY 1999 activities: FY 1999 brings to a close Phase I of our project work in the Everglades. The major activity in FY 1999 will be to complete all analyses, verify and compile data, and publish reports.
FY 1999 deliverables/products: The following products are anticipated in FY 1999:
FY 1999 outreach: The results of our research will be presented in overall project reviews (Florida DEP, SFWMD), information meetings (USGS), and scientific meetings (AGS, ASLO). Data and results are shared freely with other INATURES projects working in South Florida through project meetings, USGS Open-tile report, and upon request.
ACCOMPLISHMENTS, OUTCOMES, PRODUCTS, OUTREACH
A final field trip planned for June-July, 1998 will bring to completion the intensive field sampling phase of the project.The stable isotopic composition of isolates and plant materials from the Everglades is being investigated in collaboration with Carol Kendall. Results of this research indicate that the isotopic link between plant materials and DOC are not straight forward, suggesting that different compound classes within the plants contribute in different ways to the DOC pool. This work will lead to better understanding of carbon cycling and food web dynamics in the Everglades.
The development of clean sampling techniques for DOC isolates continued in collaboration with Jim Hurley of Wisconsin DNR. A variety of cleaning procedures and resin types have been tested to minimize Hg contamination of the isolates and fractions. Field testing will be carried out during the summer 1998 field trip. Work continues on the distribution of Hg to the higher MW fractions of the DOC (determined by ultrafiltration). In collaboration with Hurley and Krabbenhoft, field and laboratory experiments to better define the photochemical behavior of Hg and DOC were designed.
The nature of organic sulfur in hydrophobic acid isolates of organic matter from various sites in the Everglades was investigated using XANES analysis at Brookhaven National Labs. Reduced sulfur containing functional groups, such as thiols, are assumed to play a major role in the binding of Hg by DOC, however, these functional groups are difficult to define by conventional techniques. XANES analyses indicate that approximately 50% of the sulfur associated with the isolates occurs as reduced sulfur.
Laboratory analyses designed to determine Hg-DOC binding constants continued in FY 98. Partially funded by the EPA, this research is an important element of our Hg-DOC work in the Everglades. Results of ion exchange binding measurements, and cinnabar dissolution and formation experiments indicate that Hg interacts strongly with organic matter isolated from the Everglades, with samples from the more eutrophic areas interacting more strongly than those from more pristine sites.
Finally, efforts continued to integrate Hg-DOC binding constants into chemical speciation models. Hg species distributions in the presence of fulvic acid were estimated with a discrete site-electrostatic model. These estimates agreed with published data. Species distributions calculated with this model were used to It estimate apparent binding constants at site U3 in WGA-2A. Apparent constants were incorporated into the MINTEQ database of the program PHREEQCI to evaluate fulvic acid-sulfide competition for Hg binding. Preliminary results indicate that reduced sulfur groups associated with fulvic acid compete with sulfide ion for Hg at higher sulfide concentrations, and, at low sulfide concentrations, Hg speciation will be dominated by fulvic acid complexation.
FY 1998 deliverables, products completed:
2. (Abstract) Aiken, G. and Reddy, M., 1997, Dissolved organic carbon in the Everglades, Florida, in U.S. Geological Survey Program on the South Florida Ecosystem-Proceedings of the Technical Symposium in Ft. Lauderdale, Florida, August 25-27, 1997, U. S. Geological Survey Open-File Report 97-385, p. 4. Poster presented at the meeting.
3. (Abstract) Reddy, M. and Aiken, G., 1997, Speciation and fractionation modeling studies - dissolved organic carbon (DOC)- mercury interaction, in U.S. Geological Survey Program on the South Florida Ecosystem-Proceedings of the Technical Symposium in Ft. Lauderdale, Florida, August 25-27, 1997, U. S. Geological Survey Open-File Report 97-385, p. 73. Poster presented at the meeting.
4. Charlton, S. R., Macklin, C. L., and Parkhurst, D. L., 1997, "PHREEQCI- A graphical user interface for the geochemical computer program PHREEQC, U. S. Geological Survey Water-Resources Investigations Report 97-4222.
5. Hurley, J. P., Krabbenhoft, D. P., Cleckner, L. B., Olson, M. L., Aiken, G, R. and Rawlic, P., 1998, Systems controls on aqueous mercury distribution in the Northern Everglades, Biogeochemistry, vol. 40, pp. 293-3 10
6. (Abstract) Aiken, G. R., Reddy. M., Tregellas, J., and Ravichandran, M., Dissolved organic carbon in the Everglades, Florida, presented during the Symposium on Refractory Organic Substances in the Environment, Oct. 6-8, 1997, University of Karlsruhe, Germany.
7. (Abstract) Aiken, G. R., Recent developments in Everglades dissolved organic carbon characterization and mercury complexation, presented by M. Reddy at South Florida Mercury Science Program Annual Workshop, West Palm Beach, May 18-20,1998
8. (Abstract) Reddy, M. M., Recent developments in modeling mercury fractionation, presented at South Florida Mercury Science Program Annual Workshop, West Palm Beach, May 18-20, 1998
9. (Abstract) Harvey, J. W., Krupa, S. L., Mooney, R. H., and Schuster, P., Are groundwater and surface water in the northern Everglades connected by vertical hydrologic fluxes through peat? 1998 AGU Spring Meeting, May 26-29. 1998, Boston, MA.
10. (Abstract) Reddy, M. M. and Aiken, G R., Speciation and fractionation modeling studies-dissolved organic carbon (DOC)- mercury interaction, presented at the 1998 AGU Spring Meeting, May 26-29, 1998, Boston, MA.
11. (Abstract) Aiken, G. and Reddy, M., 1997, Dissolved organic carbon in the Everglades, Florida, in U.S. Geological Survey Program on the South Florida Ecosystem 1998 AGU Spring Meeting, May 26-29, 1998, Boston, MA.
12. (Abstract) Ravichandran, M., Aiken, G. R., Reddy, M. M., and Ryan, N., Enhanced dissolution of cinnabar (mercuric sulfide) by dissolved organic matter from the Florida Everglades, 1998 AGU Spring Meeting, May 26-29, 1998, Boston, MA.
13. (Abstract) Hoch, A. R., Reddy, M. M., and Aiken, G. R., Inhibition of calcite growth by natural organic material from the Florida Everglades at pH = 8.5 and 250,1998 AGU Spring Meeting, May 26-29, 1998, Boston, MA.
14.(Abstract) Schuster, P.F., Reddy, M. M., Aiken, G. R., Hurley, J.. and Krabbenhoft, D.F., Diel sulfide and dissolved oxygen concentration gradients at two sites in the Everglades, 1998 AGU Spring Meeting, May 26-29, 1998, Boston, MA.
15. (Abstract) Hurley, J.P., Krabbenhoft, D.P., Schuster, P. F., Olson, M., Cleckner, L., and Aiken, G.R., Development of a conceptual model of the Everglades mercury cycle: Results from diel studies, 1998 AGU Spring Meeting, May 26-29, 1998, Boston, MA.
16.(Abstract) Krabbenboft, D.P., Hurley, J.P., Aiken, G.R., Olson, M., Dewild, J., Cleckner, L., Lindberg, S., and Grimshaw, J., The influence of photochemical processes on the Everglades mercury cycle, 1998 AGU Spring Meeting, May 26-29, 1998, Boston, MA.
17.(Extended abstract) Ravichandran, M., Aiken, G.R., Reddy, M.M., and Ryan, J.N., Enhanced dissolution of cinnabar (mercuric sulfide) by dissolved organic matter from the Florida Everglades, 216th American Chemical Society Meeting, Aug. 1998, Boston, MA.
18. (Extended abstract, invited talk) Aiken, 0., Ravichandran, M., Reddy, M. M., Ryan, J.N, and Tregellas, J., Interactions of dissolved organic carbon with mercury in the Everglades, Florida 216th American Chemical Society Meeting, Aug. 1998, Boston, MA.
19. (Extended abstract) Hoch, A.K, Reddy, M.M,, and Aiken, G.R., Inhibition of calcite growth by natural organic material from the Florida Everglades at pH=8.5 and 250C 216, American Chemical Society Meeting, Aug. 1998, Boston, MA.
20.(Journal article) Ravichandran, M., Aiken, G.R., Reddy, M.M., and Ryan, J.N., Enhanced dissolution of cinnabar (mercuric sulfide) by dissolved organic matter from the Florida Everglades, submitted for director's approval for submission to Environmental Science and Technology