Water Resources Research Act Program

Details for Project ID 2010AR248B

Determination of the magnitude of mercury methylation in the water column of a high organic carbon river, lower Ouachita River, Union and Ashley Counties, Arkansas

Institute: Arkansas
Year Established: 2010 Start Date: 2010-03-01 End Date: 2011-02-28
Total Federal Funds: $19,761 Total Non-Federal Funds: $39,524

Principal Investigators: Phil Hays, Stephen Boss, John Brahana, Ralph K. Davis

Project Summary: Conventional approaches to mercury (Hg) methylation research in riverine systems have focused on processes below the sediment-water interface, where redox conditions are most favorable for the conversion of inorganic Hg (Hg II) to methylmercury (MeHg) by anaerobic bacteria (Benoit, et al. 1999) . However, recent studies in marine systems have shown a positive correlation between dissolved organic carbon (DOC) and MeHg in the water column, suggesting the important role of organic carbon in the production of MeHg (Sunderland, et al. 2009). This study will build on these and other findings and investigate the potential for Hg methylation in the water column of a stratified, high organic content river in south Arkansas. The Ouachita River in Union and Ashley Counties in south Arkansas contains five river segments listed as impaired water bodies by the Environmental Protection Agency (EPA) for Hg in fish tissue, and fish consumption advisories are currently implemented for these segments. As there are few data available for Hg and MeHg in water in the state of Arkansas, a comprehensive characterization of Hg and MeHg is necessary to assess the controls on toxic MeHg production in this impaired river. Historical data reflecting high concentrations of DOC for the lower Ouachita River and high concentrations of MeHg in fish tissue make this system an important candidate to investigate the potential link between DOC and MeHg. To assess the distribution and production of MeHg in the lower Ouachita River, water and sediment samples will be collected at three sites during the summer of 2010 and analyzed for Hg and MeHg. The study will use state-of-the-science Hg-specific low-level sampling protocols and analytical methods. These data will be used to ascertain the contribution of MeHg from the water column of the lower Ouachita River while providing a comprehensive characterization of mercury distribution in this river, providing important information regarding mercury contamination in the state of Arkansas.