Uranium Transformations in Static Microcosms

Elucidation of complex biogeochemical processes and their effects on speciation of U in the subsurface is critical for developing remediation strategies with an understanding of stability. We have developed static microcosms that are similar to bioreduction process studies in situ under laminar flow...

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Bibliographic Details
Published in:Environmental science & technology 2009-01, Vol.441 (2)
Main Authors: Kelly, Shelly D, Wu, Weimin, Yang, Fan, Criddle, Craig, Marsh, Terence, O'Loughlin, Edward J., Ravel, Bruce, Watson, David B, Jardine, Philip M, Kemner, Kenneth M
Format: Article
Language:English
Subjects:
ABSORPTION
BINDING ENERGY
ELECTRONS
FINE STRUCTURE
LAMINAR FLOW
MICROCOSMS
NUCLEAR FUEL CYCLE AND FUEL MATERIALS
SEDIMENTS
SPECTROSCOPY
STABILITY
SULFATES
TRANSFORMATIONS
URANINITES
URANIUM
VALENCE
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Summary:Elucidation of complex biogeochemical processes and their effects on speciation of U in the subsurface is critical for developing remediation strategies with an understanding of stability. We have developed static microcosms that are similar to bioreduction process studies in situ under laminar flow conditions or in sediment pores. Uranium L{sub 3}-edge X-ray absorption near-edge spectroscopy analysis with depth in the microcosms indicated that transformation of U{sup VI} to U{sup IV} occurred by at least two distinct processes. Extended X-ray absorption fine structure (EXAFS) analysis indicated that initial U{sup VI} species associated with C- and P-containing ligands were transformed to U{sup IV} in the form of uraninite and U associated with Fe-bound ligands. Microbial community analysis identified putative Fe{sup III} and sulfate reducers at two different depths in the microcosms. The slow reduction of U{sup VI} to U{sup IV} may contribute the stability of U{sup IV} within microcosms at 11 months after a decrease in bioreducing conditions due to limited electron donors.
ISSN:0013-936X
1520-5851