Collaborative Research: Mercury Cycling in Soils: Dynamic Sources for Aquatic Environments

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Lyons9975414The biogeochemistry of mercury in aquatic systems has received considerable attention because of the toxicity and biomagnification of methylmercury. However, much of the methylmercury entering water bodies is derived from soils. This program will utilize a multidisciplinary approach to investigate factors controlling mercury methylation in soils and its transport into aquatic systems using the Carson River, Nevada as the test site. Field and laboratory investigations will include analysis of mercury speciation, measurements of methylation, demethylation, and reduction of mercury, the distribution and expression of bacterial genes responsible for mercury transformations, and application of a mercury biosensor for investigating mercury bioavailability. Manipulative experiments will be conducted to determine effects of wetting and drying cycles and oxygen availability on pathways of mercury cycling. The biogeochemical/molecular results will be used to greatly improve a mercury transport model, which will be tested empirically during low and high flow conditions. The results will delineate controls on net methylmercury formation and eventual transport in a contaminated site, and will be useful for understanding the role of soils in controlling methylmercury pollution in general.This proposal was submitted in response to the Environmental Geochemistry and Biogeochemistry solicitation NSF 99-9, and is being funded jointly by the Divisions of Chemistry, Earth Sciences, and Ocean Sciences.