The formation and transport of methylmercury (MeHg), a neurotoxin, in aquatic environments is a global concern for human health as MeHg can bioaccumulate and biomagnify to high concentrations in aquatic food webs. MeHg is formed by conversion from inorganic mercury through microbial mediated methylation. Sulfate-reducing bacteria have been identified as the primary organisms responsible for MeHg production. Pure-culture studies suggest that low availability of cobalt and copper may inhibit mercury methylation, but whether such limitations occur in the environment is unclear. In this study, mercury methylation in sediments from the East Fork Poplar Creek in Oak Ridge, Tennessee were incubated in the presence and absence of added dissolved cobalt. This section of the creek contains elevated mercury concentrations in the sediments due to industrial contamination and the rates and controls on methylation have been studied extensively. Two levels of cobalt addition to the sediment incubations were investigated to reach target dissolved concentrations within the range suggested to be ideal for MeHg production in pure culture studies. These concentrations were estimated from preliminary measurements of cobalt binding by the sediments. Sulfide was generated over the 72 hour incubation period indicating that sulfate-reducing bacteria were active. MeHg concentrations increased over the time period studied with no noticeable enhancement of methylation resulting from the addition of cobalt. Methylation and demethylation rates both decreased with increasing cobalt concentrations. Overall, cobalt appeared to either inhibit or have no effect on mercury methylation in the sediments. These initial results suggest that mercury methylation in natural systems may not be cobalt-limited but future work is needed to evaluate a broader range of cobalt additions, to more robustly assess cobalt bioavailability, and to explore longer incubation times.

Impact of cobalt on mercury methylation in East Fork Poplar Creek, Oak Ridge, Tennessee

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.