HR: 0830h
AN: B21C-0728    [PDF]
TI: Bacterial Reduction of Uranium in Mineralogically Heterogeneous Media: Impact of Mn- and Fe-oxides.
AU: * Ginder-Vogel, M A
EM: gindervm@stanford.edu
AF: Stanford University, Dept. of Geology Braun Hall, MC 2115, Stanford, CA 94305 United States
AU: Fendorf, S
EM: fendorf@stanford.edu
AF: Stanford University, Dept. of Geology Braun Hall, MC 2115, Stanford, CA 94305 United States
AB: Dissimilatory reduction of uranium can have a profound impact on the transport of uranium within surface and subsurface environments. The rate and extent of biological uranium reduction, and stability of reduced uranium phases, will be influenced by sediment mineralogy. Both Fe- and Mn-oxide phases have the potential to retard U(VI) reduction and may even serve as oxidants of reduced U phases such as uraninite. Mn-oxides in particular may serve as oxidants of uranium. Here we examine the rate of uranium reduction in the presence of Fe- and Mn-oxide coated sands and the spatial relationship of both products and reactants, inclusive of bacterial cells. Solids were characterized using X-ray absorption and Raman spectroscopies while spatial relationships between minerals and microbes were resolved using electron microscopies and X-ray microspectroscopy. The presence of birnessite decreases the rate and extent of biological uranium reduction while ferrihydrite only retards the rate of reduction. Uranium reduction rates also vary with birnessite concentration. During in-situ bioremediation aqueous uranium concentrations and uraninite stability will be partially determined by subsurface mineralogy.
DE: 0330 Geochemical cycles
SC: Biogeosciences [B]
MN: 2003 Fall Meeting