Reactivity of Nano-Biogenic Uraninite in the Subsurface: Dissolution Rates and Mechanisms

Bargar, J. R. et al. (2010) Reactivity of Nano-Biogenic Uraninite in the Subsurface: Dissolution Rates and Mechanisms. In: Goldschmidt 2010, Knoxville, TN USA, 13-18 June 2010,

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Biogenic uraninite is of potentially great significance to naturally and artificially bioreduced sediments and uranium ore deposits. The stability of this phase is believed to be compromised by its nano size. Since other forms of U (IV) are thought to be more prone to oxidation than uraninite, the stability of this solid can be viewed as a limiting case, a firstorder scientific question likely to impact the success of stimulated bioremediation approaches. Trace and major-ion solutes strongly moderate uraninite stability, and their spatial/temporal variability in groundwater is difficult to capture in laboratory analog studies. Evaluation of kinetic parameters for nano-biogenic-uraninite dissolution in the field and meaningful testing of hypotheses developed from previous laboratory work therefore requires stability studies under bona fide groundwater conditions. Consequently, biogenic uraninite corrosion by molecular oxygen was studied in groundwater at Rifle, Colorado. The Rifle IFRC site is ideal for such investigations because of the availability of wells with contrasting DO concentrations, extensive historical groundwater data, and good site infrastructure. Nano-uraninite synthesized by U (IV) reduction by proteobacteria isolated from Rifle groundwater was deployed in wells and subsequently analyzed to assess dissolution rates and compositional/structural changes. Net U loss is remarkably slow, at least 100-fold slower than those obtained in laboratory experiments, and is impacted by associated organic matter. Fundamental controls over this behavior will be discussed. This study indicates that nano-biogenic uraninite is relatively stable in groundwater, even under oxic conditions.

Item Type:Conference Proceedings
Glasgow Author(s) Enlighten ID:Veeramani, Dr Harish
Authors: Bargar, J. R., Campbell, K. M., Veeramani, H., Stubbs, J. E., Lezama-Pacheco, J. S., Suvorova, E. I., Ulrich, K.-U., Blue, L., Bernier-Latmani, R., Giammar, D. E., Yabusaki, S. B., and Long, P. E.
College/School:College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
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