SS4.02 The Role of Microbiology in Trace Metal and Organic Contaminant Cycling in Aquatic Systems
Date: Wednesday, June 12, 2002
Location: Poster Session - VCC
 
AgeeJL, United States Geological Survey, Menlo Park, USA, jlagee@usgs.gov
Marvin-DiPasquale, M, , United States Geological Survey, Menlo Park, USA, mmarvin@usgs.gov
 
A COMBINED RADIOTRACER AND SEQUENTIAL EXTRACTION APPROACH USED TO EXAMINE THE DISTRIBUTION OF INORGANIC AND ORGANIC MERCURY IN WHOLE SEDIMENT
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The use of radiotracers to measure rates of microbial methylmercury (MeHg) production and degradation has become increasingly common. However, the degree to which radiotracer amendments mimic the distribution and microbial availability of in-situ inorganic mercury (Hg(II)) or MeHg is typically unknown. We examined this in Carson River sediments by combining radiotracer (203Hg(II) and 14C-MeHg) amendments with a sequential extraction approach to determine how the two mercury forms distribute themselves among three readily extractable pools: water, weak-acid, and weak-base. Total extractable 203Hg(II) and 14C-MeHg pool sizes varied widely as a function of sediment type (12-83 % and 27-85 % respectively). The trend in % recovery (weak-base > water > weak acid) was similar for both 203Hg(II) and in-situ total-Hg. However, a larger fraction of the 203Hg(II) was readily extractable compared with in-situ total-Hg. The % 14C-MeHg recovered with weak acid decreased as a function of increasing sediment reduced sulfur and organic matter, while the opposite trend was observed with weak base. The results demonstrate that combined radiotracer and sequential extraction techniques can be useful in elucidating mercury species availability for microbial transformations.