Wednesday, November 7, 2007
324-9
Comparison of Mercury and Methyl Mercury Concentration of Sediments from a Sandy (Georgia) and Muddy (Louisiana) Coast.
John R. White1, Ron DeLaune1, and Chunyan Li2. (1) Wetland Biogeochemistry Institute, Louisiana State University, 3239 Energy, Coast & Environment Bld, Dept. of Oceanography & Coastal Sciences, Baton Rouge, LA 70803, (2) Coastal Studies Institute, Louisiana State University, 208 Howe-Russell Hall, Department of Oceanography & Coastal Sciences, Baton Rouge, LA 70803
Elevated mercury, in particular, methyl mercury poses both ecological and health risks. There is a paucity of information on the mercury concentrations of continental shelf sediments. Shelf sediments off the Atchafalaya River, LA are fine grained muds (predominantly silt and clay) which differ from the clean, quartz sand shelf sediments off the coast of Georgia (87% sand). We investigated total and methyl Hg concentrations of sediments in transects from off the Louisiana and Georgia coastlines. Additional sediment properties measured include: percent organic matter, total carbon, total nitrogen, total phosphorus, bulk density, and grainsize (%sand-silt-clay). On average, total Hg concentrations were 4 times higher in the mud sediments along the LA coast (34.9 ppb) than the sandy sediments of the GA coast (8.76 ppb). However, methyl Hg was only 2 time higher in the LA coastal sediments (0.23 ppb) than the GA coast (0.11 ppb). Methyl Hg was strongly correlated with organic matter in the GA sediments while not in the mud sediments while methyl Hg was correlated with total Hg in the LA mud sediment but not in the GA sediments. Results suggest that organic matter controls methyl Hg concentrations in very low organic matter sediments while in the more organic, fine grained sediments, total Hg appeared to control methyl Hg concentrations.