Environ. Sci. Technol. 2008, 42, 8709–8714
Indirect UO2 Oxidation by Mn(II)-oxidizing Spores of Bacillus sp. Strain SG-1 and the Effect of U and Mn Concentrations S A T Y A V A T H I C H I N N I , * ,† CRAIG R. ANDERSON,† KAI-UWE ULRICH,‡ DANIEL E. GIAMMAR,‡ AND BRADLEY M. TEBO† Division of Environmental and Biomolecular Systems, Oregon Health & Science University, 20000 NW Walker Road, Beaverton, Oregon-97006, and Department of Energy, Environmental and Chemical Engineering, Washington University, St. Louis, MO
Received May 19, 2008. Revised manuscript received September 1, 2008. Accepted September 10, 2008.
Manganese oxides are widespread in the environment and their surface reactivity has the potential to modify the geochemical behavior of uranium. We have investigated the effect of different concentrations of U and Mn on the coupled biogeochemical oxidation-reduction reactions of U and Mn. Experiments conducted in the presence of Mn(II)-oxidizing spores from Bacillus sp. strain SG-1 and 5% headspace oxygen show that the Mn oxides produced by these spores can rapidly oxidize UO2. Thirty to fifty times more UO2 is oxidized in the presence of Mn oxides compared to Mn oxide free controls. As a consequence of this UO2 oxidation, Mn oxides are reduced to soluble Mn(II) that can be reoxidized by SG-1 spores. SG-1 spores cannot directly oxidize UO2, but UO2 oxidation proceeds rapidly with Mn(II) concentrations of
