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Site Biogeochemical Processes and Microcosm Studies

Site investigation and geochemical modeling provides the key information on major chemical species and microbial communities involved in Hg biogeochemical transformations in water and sediment. We will focus our immediate attention at the upper East Fork Poplar Creek at Oak Ridge where field studies will identify key processes and establish the range of geochemical conditions in which critical transformations take place. The field information obtained will be used in abiotic and microbial genetics studies. Expert consultation will be used in the early stage of the study to identify key knowledge gaps with regard to the observed Hg speciation in the context of local geology and water chemistry. In parallel with site investigation studies, we will quantify Hg reactivity in the upper East Fork Poplar Creek system, conduct methylation bioassays with pure cultures of methylating bacteria, conduct microcosm studies of Hg transformation in ecologically intact systems, and make in situ measurements of methyl mercury production in manipulative field experiments. The functional gene arrays developed under Microbial Transformations and Genetics will be used for field and microcosm samples. Data analysis, integration, geochemical modeling, and site conceptual and numerical modeling will also be integrated here.