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Microbial mercury cycling in sediments of the San Francisco Bay-Delta

December 1, 2003

Microbial mercury (Hg) methylation and methylmercury (MeHg) degradation processes were examined using radiolabled model Hg compounds in San Francisco Bay-Delta surface sediments during three seasonal periods: late winter, spring, and fall. Strong seasonal and spatial differences were evident for both processes. MeHg production rates were positively correlated with microbial sulfate reduction rates during late winter only. MeHg production potential was also greatest during this period and decreased during spring and fall. This temporal trend was related both to an increase in gross MeHg degradation, driven by increasing temperature, and to a build-up in pore water sulfide and solid phase reduced sulfur driven by increased sulfate reduction during the warmer seasons. MeHg production decreased sharply with depth at two of three sites, both of which exhibited a corresponding increase in reduced sulfur compounds with depth. One site that was comparatively oxidized and alkaline exhibited little propensity for net MeHg production. These results support the hypothesis that net MeHg production is greatest when and where gross MeHg degradation rates are low and dissolved and solid phase reduced sulfur concentrations are low.

Publication Year 2003
Title Microbial mercury cycling in sediments of the San Francisco Bay-Delta
DOI 10.1007/BF02803660
Authors Mark Marvin-DiPasquale, Jennifer L. Agee
Publication Type Article
Publication Subtype Journal Article
Series Title Estuaries
Index ID 70185658
Record Source USGS Publications Warehouse
USGS Organization Toxic Substances Hydrology Program