Associate Professor, Department of Environmental Sciences, Earth and Planetary Sciences, Rutgers University
Abstract: The disposal of mercury (Hg) containing wastes has contaminated large areas of sediment and groundwater in the United States. When released into the environment, Hg undergoes redox transformations that strongly affect its solubility and sorption characteristics. Dissolved gaseous elemental mercury [Hg(0)] is mobile in groundwater, while oxidized ionic mercury [Hg(II)] readily sorbs onto mineral surfaces and natural organic matter. Furthermore, Hg(II) is the substrate for methylation and uptake of Hg(II) by anaerobic methylating bacteria leads to the production of neurotoxic methylmercury [MeHg]. Critical to predicting the impacts of subsurface Hg contamination is a mechanistic understanding of the biogeochemical processes that control mercury reduction and methylation along hydrological flow paths. In this presentation, I will discuss our research on Hg reduction and oxidation in groundwater. I will describe our recent discovery of a new pathway in the subsurface mercury cycle, whereby neurotoxic methylmercury is formed from dissolved elemental mercury by anaerobic bacteria.
Currently the redox interactions between Hg(0) and microbial biomass are poorly understood. In this study, we conducted laboratory experiments to determine if subsurface microorganisms can oxidize Hg(0) to Hg(II) under anoxic conditions.