The role of biogeochemical dynamics in the formation of U(VI) solid phases

Tracy E. Letain, Terry C. Hazen, and Heino Nitsche

Contact: Tracy E. Letain, 510/486-6612, TELetain@lbl.gov

Research Objectives
To assist the U.S. Department of Energy with long-term stewardship issues associated with bioremediation of uranium (U), the overall goal of this work is to define the mechanisms by which microorganisms facilitate the formation of U(VI) solid phases. Under anaerobic conditions, microbial reduction of U(VI) to U(IV) can potentially decrease groundwater U contamination by lowering solubility and by slowing migration through the soil. However, such biological alteration must be considered temporary unless long-term anaerobicity can be maintained. When aerobic conditions return, U(IV) will likely re-oxidize to U(VI), which is generally more soluble and potentially more mobile. The transformation to U(VI)-phosphate solids is of particular interest, since the U(VI) phosphates are the least soluble of the U(VI) solids found in nature.

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