Inhibition of bacterial U(VI) reduction by calcium

Journal Article · Thu May 01 04:00:00 EDT 2003 · Environmental Science and Technology

DOI:https://doi.org/10.1021/es0210042· OSTI ID:15007186

Brooks, Scott C; Fredrickson, Jim K; Carroll, S L; Kennedy, David W; Zachara, John M; Plymale, Andrew E; Kelly, S D; Kemner, K M; Fendorf, S

The rapid kinetics of bacterial U(VI) reduction and low solubility of uraninite (UO2,cr) make this process an attractive option for removing uranium from groundwater. Nevertheless, conditions that may promote or inhibit U(VI) reduction are not well-defined. Recent descriptions of Ca-UO2-CO3 complexes indicate that these species may dominate the aqueous speciation of U(VI) in many environments. We monitored the bacterial reduction of U(VI) in bicarbonate-buffered solution in the presence and absence of Ca. XAFS measurements confirmed the presence of a Ca-U(VI)-CO3 complex in the initial solutions containing calcium. Calcium, at millimolar concentrations (0.45-5 mM), caused a significant decrease in the rate and extent of bacterial U(VI) reduction. Both facultative (Shewanella putrefaciens strain CN32) and obligate (Desulfovibrio desulfuricans, Geobacter sulfurreducens) anaerobic bacteria were affected by the presence of calcium. Reduction of U(VI) ceased when the calculated system Eh re ached -0.046+/- 0.001 V, based on the Ca2UO2(CO3)(3) --> UO2,cr couple. The results are consistent with the hypothesis that U is a less energetically favorable electron acceptor when the Ca-UO2-CO3 complexes are present. The results do not support Ca inhibition caused by direct interactions with the cells or with the electron donor as the reduction of fumarate or Tc(VII)O-4(-) under identical conditions was unaffected by the presence of Ca.

• Research Organization: Pacific Northwest National Lab., Richland, WA (US)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 15007186
• Report Number(s): PNNL-SA-39586; KP1301010
• Journal Information: Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 9 Vol. 37; ISSN ESTHAG; ISSN 0013-936X
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
BACTERIA
BINDING ENERGY
CALCIUM
DESULFOVIBRIO
ELECTRONS
HYPOTHESIS
KINETICS
SOLUBILITY
STRAINS
URANINITES
URANIUM
VALENCE