Mark Marvin-DiPasquale Ronald Oremland 2005 spreadsheet http://sofia.usgs.gov/projects/index.php?project_url=bact_demeth Methylmercury (MeHg) degradation was investigated along an eutrophication gradient in the Florida Everglades by quantifying 14CH4 and 14CO2 production after incubation of anaerobic sediments with 14C-MeHg. Degradation rate constants (k) were consistently <=0.1 per day, and decreased with sediment depth. Higher k values were observed when shorter incubation times and lower MeHg amendment levels were used, and k increased two-fold as in-situ MeHg concentrations were approached. The average floc layer k was 0.046 +/- 0.023/ d (n=17) for 1-2 day incubations. In-situ degradation rates were estimated to be 0.02 to 0.5 ng MeHg/g dry sed/d, increasing from eutrophied to pristine areas. Nitrate-respiring bacteria did not demethylate MeHg, and NO3- addition partially inhibited degradation in some cases. MeHg degradation rates were not affected by PO4-3 addition. 14CO2 production in all samples indicated that oxidative demethylation (OD) was an important degradation mechanism. OD occurred over five orders of magnitude of applied MeHg concentration, with lowest limits (1-18 ng MeHg/g dry sediment) in the range of in-situ MeHg levels. Sulfate reducers and methanogens were the primary agents of anaerobic OD, although it is suggested that methanogens dominate degradation at in-situ MeHg concentrations. Specific pathways of OD by these two microbial groups are proposed. The objective of this research is to provide ecosystem managers with MeHg degradation rate data from a number of study sites that represent a diversity of hydrologic and nutrient regimes common to the Everglades, and to forge a better understanding of the microbial and geochemical controls regulating MeHg degradation in this system. This project ended in 1999. 199606 199612 199704 199707 199801 199806 ground condition Complete None planned -80.8 -80.2 26.7 25.2 none biogeochemistry mercury mercury cycling methylmercury sediments MeHg peat geochemistry peat soils sulfate reduction geochemistry ISO 19115 Topic Category environment geoscientificInformation inlandWaters 007 008 012 Department of Commerce, 1995, Countries, Dependencies, Areas of Special Sovereignty, and Their Principal Administrative Divisions, Federal Information Processing Standard (FIPS) 10-4, Washington, DC, National Institute of Standards and Technology United States US U.S. Department of Commerce, 1987, Codes for the identification of the States, the District of Columbia and the outlying areas of the United States, and associated areas (Federal Information Processing Standard 5-2): Washington, DC, NIST Florida FL Department of Commerce, 1990, Counties and Equivalent Entities of the United States, Its Possessions, and Associated Areas, FIPS 6-3, Washington, DC, National Institute of Standards and Technology Miami-Dade County Monroe County USGS Geographic Names Information System Everglades National Park Taylor Slough none Central Everglades Greater Lake Okeechobee SW Big Cypress Water Conservation Area 2A Water Conservation Area 3B WCA2B WCA2A WCA3A Water Conservation Area 2B none none Mark Marvin-DiPasquale U.S. Geological Survey Project manager mailing address

345 Middlefield Road, Building 15, McKelvey Building

Menlo Park CA 94025 USA 650 329 4442 650 329-4463 mmarvin@usgs.gov http://sofia.usgs.gov/exchange/marvin-dipasquale/locationmmd.html location of sites for methylmercury degradation measurements GIF MS Excel spreadsheet Marvin-DiPasquale, Mark C. Oremland, Ronald S. 1998 report Environmental Science and Technology v. 32, n. 17 Washington, DC American Chemical Society All users may view the abstract of this article. If you are a subscriber, you may view the article. If you are not a subscriber, you may purchase and download the PDF version of the article. http://pubs.acs.org/doi/abs/10.1021/es971099l Marvin-DiPasquale, Mark C. Agee, Jennifer; McGowan, Chad; Oremland, Ronald S.; Thomas, Martha; Krabbenhoft, David; Gilmour, Cynthia C. 2000 report Environmental Science and Technology v. 34 , n. 23 Washington, DC American Chemical Society All users may view the abstract of this article. If you are a subscriber, you may view the article. If you are not a subscriber, you may purchase and download the PDF version of the article. http://pubs.acs.org/doi/abs/10.1021/es0013125 not applicable not available Three years of field and laboratory studies research were completed. The specific areas of investigation are outlined below. 1) Field Measurements: Sediment cores were sectioned into three to five discrete 2 to 4 cm horizons, within hours of sample collection. Homogenized sub-samples from each horizon were transferred into crimp sealed serum vials, purged with N2 gas, and injected with radiolabeled 14CH3Hg+. After incubating anaerobically for hours to days, incubations were arrested with either acid or base, depending on the method of 14C endproduct detection. End-products (14CH4 and 14CO2 ) were measured via gas proportional counting (prior to December 1996) or a CH4 combustion / CO2 trapping method (after December 1996). Degradation rate constants are calculated from the fraction of MeHg degraded per incubation time. The relative amounts of CH4 and/or CO2 produced provides an indication as to the relative importance of MC and/or OD. Degradation rates were assessed with respect to both sediment depth and site location. 2) Nutrients and Microbial Inhibitors: The affect of nutrients (NO3-, PO4-3, NH4+) and SO4-2 on the degradation of 14CH3Hg+ was assessed by amending parallel sets of incubation samples with these substrates and processing as described above. Likewise, specific microbial inhibitors of both SRB and MPB were used to determine the relative contribution of these microbial groups to MeHg degradation. 3) The Fate of Hg: Preliminary experiments were conducted exploring the fate of Hg resulting from MeHg degradation. Vapor phase Hg(0) was collected on gold traps by flushing the head-space of samples amended and incubated with MeHg. The concentration of Hg(0) was assayed by cold vapor atomic fluorescence spectroscopy. Our initial (unpublished) results suggest that very little (> 0.01% ) of liberated Hg+2 produced as a result of MeHg degradation is reduced to volatile Hg(0). 4) Kinetic Studies: The dependence of MeHg degradation rates on MeHg amendment concentration was explored over a wide range (1-2000 ng MeH/g dry sed). The low end of this range approached natural in-situ concentrations (0.1-10 ng MeHg/g dry sed). These low levels were achieved by increasing our standard sample size from 3 to 80 cc of sediment, using a custom synthesized high-specific activity 14C-MeHg radiotracer, and employing the sensitive CH4 combustion / CO2 trapping method for 14C end-product quantification. Unknown Mark Marvin-DiPasquale U.S. Geological Survey Project manager mailing address

345 Middlefield Road, Building 15, McKelvey Building

Menlo Park CA 94025 USA 650 329 4442 650 329-4463 mmarvin@usgs.gov Data for each site includes: site name, date; sediment depth interval (cm); incubation time (days); C14-MeHg injected (ng/cc wet sed); MeHg degradation first order rate constant (k); and MeHg -degradation potential rate (ng/cc wet sed/d) USGS personnel Heather S.Henkel U.S. Geological Survey mailing address

600 Fourth St. South

St. Petersburg FL 33701 USA 727 803-8747 ext 3028 727 803-2030 hhenkel@usgs.gov methylmercury degradation rates The data have no explicit or implied guarantees. MS Excel unknown 0.041 http://sofia.usgs.gov/exchange/marvin-dipasquale/mmdindex.html Data may be downloaded from the SOFIA website. none 20090803 Heather Henkel U.S. Geological Survey mailing and physical address

600 Fourth Street South

St. Petersburg FL 33701 USA 727 803-8747 ext 3028 727 803-2030 sofia-metadata@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998 none This metadata record may have been copied from the SOFIA website and may not be the most recent version. Please check http://sofia.usgs.gov/metadata to be sure you have the most recent version.