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The Oak Ridge National Laboratory (ORNL) Science Focus Area (SFA), funded by the Department of Energy's Subsurface Biogeochemical Research program, focuses on the biogeochemical transformations that govern mercury (Hg) speciation at the sediment-water interface, and, particularly, the processes controlling the production of methyl mercury. The SFA is a multi-scale, multi-disciplinary, multi-institutional research program that integrates geochemistry, microbiology, molecular biology and molecular simulations to understand Hg behavior in the field. This research is designed to make fundamental scientific contributions to support the prediction and mitigation of mercury at Department of Energy (DOE) contaminated sites. This research is underpinned by ORNL’s strong expertise in field-to-laboratory geochemistry and microbiology, a comprehensive regional groundwater model, and world-class neutron sources and high-performance computing capabilities.

Mercury in water, sediment and biota in streams (in red) at Oak Ridge Reservation.

Mercury, a pervasive global pollutant, is a contaminant of concern on the Oak Ridge Reservation and at numerous other sites. Mercury in it's common methylated form (monomethyl mercury) bioaccumulates in the food web and is highly toxic to humans and other ecological receptors.

Mercury bioacummulation is a global concern.

Biogeochemical factors controlling methyl mercury production at DOE sites represents a serious knowledge gap. For example, data collected on the Oak Ridge Reservation show that decrease in Hg levels does not necessarily lead to decrease in aqueous methyl mercury or to its bioaccumulation in fish. This observation suggests that at the high Hg levels commonly present in highly contaminated source areas, either methyl mercury production is inhibited or demethylation significantly exceeds methylation.

ORNL is working to close the gaps in our knowledge regarding the biogeochemical transformations of mercury. Specifically we are conducting research to:

Closing these knowledge gaps will lead to new approaches to Hg remediation for DOE and the Nation.

Basic research needs: Elucidate Hg methylation processes at sediment-water interface and the controls on methyl mercury production.

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