The chemical and physical forms of U(IV), as well as the biogeochemical processes by which they form and transform, profoundly influence the behavior of uranium in reduced contaminated sediments. Obtaining such information in aquifers has been a significant scientific challenge, due to generally quite low (ppm level) concentrations of uranium, the inaccessibility of the subsurface, and the presence of multiple U species. X-ray absorption spectroscopy (XAS) has proved to be an important technique for this and related problems. We have developed an in-situ approach to studying U(IV) species in the Old Rifle, Co, aquifer using XAS coupled to electron microscopy and chemical extraction techniques. A variety of U(IV) species have been observed and will be discussed. These studies are providing new information about U(IV) dynamics under conditions in the Old Rifle aquifer and are informing the development of improved biogeochemical models for uranium behavior in complex subsurface systems.

Uranium(VI) reduction products in the Old Rifle, CO alluvial aquifer: Insights from X-ray absorption spectroscopy

244th National Meeting (2012)

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