Spectroscopic Study of Uranium (VI) Reduction by Plant Biomass

Uranium is a common and problematic groundwater contaminant at Department of Energy legacy sites. At the former uranium ore processing plant at Rifle, Colorado, sediments rich in decayed plant biomass contain large concentrations of uranium that are slowly being released back to the aquifer. To simulate the reaction that occurs in organic rich sediments of the Rifle aquifer, biomass was incubated in U (VI) bearing groundwater. Carbon X-ray absorption spectroscopy (XAS) was then used to measure if uranium was bound to the biomass. When uranium binds to biomass the peaks in the C XAS spectra will change shape. Uranium LIII-edge XAS was used to determine the oxidation state of uranium. It was observed that the uranium added to the biomass was reduced to uranium (IV), however no change was seen in the C XAS bands. This supports that biomass does reduce uranium, however uranium was possibly bound to too low of a percentage of the total carbon in the biomass for it to be seen in the C XAS results