Natural organic matter profoundly influences the biogeochemical cycling of iron and sulfur and the behavior of uranium in contaminated aquifers. In the subsurface, under conditions where organic carbon is present and dissolved oxygen is low or absent, organic carbon drives the reduction of uranium, leading to a decrease in its groundwater concentration due to the relatively insoluble nature of U(IV). In contaminated aquifers in the Western U.S., such as the Old Rifle, CO site, natural reduction of uranium by particulate organic carbon in low permeability sediments has been implicated as a factor maintaining persistent uranium groundwater plumes. In order to better understand the reaction networks controlling uranium mobility, it is essential to know the molecular-scale speciation of U, Fe, S and C in such reduced sediments. X-ray absorption spectroscopy and microscopy are used to study these elements speciation and distribution within sediments from the Old Rifle, CO, aquifer.

Biogeochemical cycling of organic carbon, uranium, and sulfur in an alluvial aquifer

245th National Meeting (2013)

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