HR: 0800h
AN: B11B-0399    [Abstracts]
TI: Explorating coupled production of dissolved organic material and methyl mercury in a tidal wetland using the intrinsic chemical composition of the organic material
AU: * Bergamaschi, B A
EM: bbergama@usgs.gov
AF: US Geological Survey, 6000 J St, Sacramento, CA 95819, United States
AU: Fleck, J A
EM: jafleck@usgs.gov
AF: US Geological Survey, 6000 J St, Sacramento, CA 95819, United States
AU: Downing, B
EM: bdowning@usgs.gov
AF: US Geological Survey, 6000 J St, Sacramento, CA 95819, United States
AU: Stephenson, M
EM: mlstephenson@mlml.calstate.edu
AF: California Dept. of Fish and Game, 7544 Sandholdt Rd., Moss Landing, CA 95039, United States
AU: Hernes, P J
EM: pjhernes@ucdavis.edu
AF: University of California at Davis, 1 Shields Ave., Davis, CA 95616, United States
AU: Boss, E
EM: emmanuel.boss@maine.edu
AF: University of Maine, School of Marine Sciences, Oreno, ME 04469, United States
AB: Elevated methyl mercury (MeHg) levels found in biota of the San Francisco Estuary have been attributed to methylation processes in the peat-rich tidal wetlands of the Estuary, where the concentration of dissolved organic matter (DOM) is tightly coupled to that of MeHg (r2=0.95). We sought to understand the geochemical processes that contribute to MeHg production by examining the composition of the co-occurring DOM. We measured spectral absorbance and fluorescence properties of DOM, as well as intrinsic chemical properties such as isotopic composition, lignin content, carbohydrate content, and bulk chemical functionality (by CPMAS-NMR). Carbon quality parameters independent of concentration such as specific UV absorbance, lignin abundance, aromatic content, biodegradability, and others were closely coupled to MeHg concentrations. This coupling, combined with the hydrologic forcing within the wetland, suggest that the zones of MeHg production are biogeochemically related to the zones of DOM release, thus providing a means to examine the underlying processes. The observed relationships were robust through the winter, spring, and fall seasons, despite a three- fold variation in MeHg and DOM concentration. The pattern of variation suggests sources of DOM and MeHg within peat pore waters rather than within the litter layer or water column. The various relationships with individual parameters will be discussed.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0416 Biogeophysics
DE: 0442 Estuarine and nearshore processes (4235)
DE: 0478 Pollution: urban, regional and global (0345, 4251)
DE: 0497 Wetlands (1890)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting