Methylmercury concentrations and production rates across a trophic gradient in the northern Everglades

摘要: Methylmercury (MeHg) concentrations and production rates were examined along with sulfur biogeochemistry in Everglades sediments March, July December, 1995, as part of a large, multi-investigator study, the Aquatic Cycling Mercury (ACME) project. The sites constitute trophic gradient, generated from agricultural runoff, across Nutrient Removal (ENR) Area, which is re-constructed wetland, Water Conservation Areas (WCA) 2A, 2B 3 northern Everglades. MeHg %MeHg (MeHg percent total Hg) lowest more eutrophic areas highest pristine south. ranged 0.1 ng gdw 1 sediment ENR to 5 WCA3 sediments; constituted 0.2% Hg (Hg T) ENR, but up about 2% two WCA2B WCA3. Methylation surficial sediments, estimated using tracer-level injections 203 Hg(II) into intact cores, 0 0.12 d , or 10 g when per day values are multiplied by ambient concentration. was generally maximal at within centimeters surface, never observed water overlying cores. spatial pattern matched that coincident distributions its suggest situ controls concentration, concentration can be used an analog for production. In addition, matches biota, suggesting bioaccumulation may predominantly function de novo methylation rate sediments. Sulfate pore waters (up 400 m), microbial sulfate-reduction 800 nm cc ) resultant sulfide 300 m) all high relative most freshwater systems. All declined south, sulfate central resembled those oligotrophic lakes (50-100 m). inversely related reduction sulfide. Control appears mimic estuary, where produced inhibits