Benoit, J. M. The University of Maryland, benoit@acnatsci.org
Mason, R. M. The University of Maryland, mason@cbl.umces.edu
Gilmour, C. C. The Academy of Natural Sciences, gilmour@acnatsci.org

 
ESTIMATION OF MERCURY-SULFIDE SPECIATION AND BIOAVAILABILITY IN SEDIMENT PORE WATERS USING OCTANOL-WATER PARTITIONING
 
An inverse relationship between pore-water sulfide concentration and bulk sediments methylmercury concentration has been observed in aquatic ecosystems. Furthermore, sulfide has been shown to have an inhibitory effect on Hg methylation by sulfate reducing bacteria. We hypothesize that uptake of inorganic Hg prior to methylation occurs via passive diffusion across the cell membrane, so the observed inhibition can be explained by a decrease in neutral dissolved Hg species with increasing sulfide. This hypothesis was tested by measuring changes in the octanol-water partitioning of inorganic mercury across a sulfide concentration gradient from 1 uM to 10 mM. Thermodynamic modeling indicated that the neutral dissolved HgS complex dominated at low sulfide but was replaced by charged disulfide species as sulfide concentration increased. The overall partitioning coefficient for Hg decreased in a manner that could be predicted based on the concentration of this complex. These results are consistent with decreased bioavailability of Hg to methylating bacteria in sediments with sulfidic pore waters.
 
Day: Wednesday, Feb. 3
Time: Poster
Location: Sweeney Center
 
Code: SS28WE0530S