![]() ![]() ![]() The study was performed at the Cottage Grove Reservoir located 15 km downstream of the historical Black Butte Hg mine. The objective of our study was to understand the role of on-going water-level fluctuations on sediment MeHg concentrations and sulfur speciation within a reservoir 75 years after initial impoundment. Much less is known about the longer-term water-level management impacts on Hg cycling in older reservoirs. This impact is most pronounced in newly created reservoirs where methylation is fueled by the decomposition of flooded organic material, which can release Hg and enhance microbial activity. Throughout North America, reservoirs tend to have elevated methylmercury (MeHg) concentrations compared to natural lakes and rivers. Mercury is methylated by anaerobic microorganisms such as sulfate reducing bacteria (SRB) in water and sediment. Mercury (Hg) is a pollutant of global concern due to its ability to accumulate as methylmercury (MeHg) in biota. Our objective was assessed by collecting seasonal measurements of total-Hg (THg) and MeHg and several ancillary parameters from the reservoir sediment and water-column, as well as water samples upstream and at the reservoir outflow. The objective of this study was to identify the role of ongoing water level fluctuations on MeHg production within the sediment of an old reservoir. This work begin to fill in necessary information required to develop optimum reservoir management practices that fullfill the needs of the immediate community (flood water management, irrigation, drinking water source) while minimizing negative environmental impacts associated with historical inputs of mercury. The topic of reservoir management and the enhancement of methyl mercury production is currently an important issue facing Region 9 and 10. ![]() The research was conducted on the Cottage Grove Reservoir (Black Butte Mine Superfund Site OU-3). This marks the first work conducted by ORD (ETSC) and Region 10 into the impacts of reservoir management on the production of methyl mercury. ![]()
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