Influences of Organic Carbon Supply Rate on Uranium Bioreduction in Initially Oxidizing, Contaminated Sediment [electronic resource].
- Published:
- Berkeley, Calif. : Lawrence Berkeley National Laboratory, 2008.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy. - Additional Creators:
- Lawrence Berkeley National Laboratory and United States. Department of Energy. Office of Scientific and Technical Information
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- Restrictions on Access:
- Free-to-read Unrestricted online access
- Summary:
- Remediation of uranium (U) contaminated sediments through in-situ stimulation of bioreduction to insoluble UO₂ is a potential treatment strategy under active investigation. Previously, we found that newly reduced U(IV) can be reoxidized under reducing conditions sustained by a continuous supply of organic carbon (OC) because of residual reactive Fe(III) and enhanced U(VI) solubility through complexation with carbonate generated through OC oxidation. That finding motivated this investigation directed at identifying a range of OC supply rates that is optimal for establishing U bioreduction and immobilization in initially oxidizing sediments. The effects of OC supply rate, from 0 to 580 mmol OC (kg sediment)⁻¹ year⁻¹, and OC form (lactate and acetate) on U bioreduction were tested in flow-through columns containing U-contaminated sediments. An intermediate supply rate on the order of 150 mmol OC (kg sediment)⁻¹ year⁻¹ was determined to be most effective at immobilizing U. At lower OC supply rates, U bioreduction was not achieved, and U(VI) solubility was enhanced by complexation with carbonate (from OC oxidation). At the highest OC supply rate, resulting highly carbonate-enriched solutions also supported elevated levels of U(VI), even though strongly reducing conditions were established. Lactate and acetate were found to have very similar geochemical impacts on effluent U concentrations (and other measured chemical species), when compared at equivalent OC supply rates. While the catalysts of U(VI) reduction to U(IV) are presumably bacteria, the composition of the bacterial community, the Fe reducing community, and the sulfate reducing community had no direct relationship with effluent U concentrations. The OC supply rate has competing effects of driving reduction of U(VI) to low solubility U(IV) solids, as well as causing formation of highly soluble U(VI)-carbonato complexes. These offsetting influences will require careful control of OC supply rates in order to optimize bioreduction-based U stabilization.
- Report Numbers:
- E 1.99:lbnl-1695e
lbnl-1695e - Other Subject(s):
- Note:
- Published through SciTech Connect.
06/10/2008.
"lbnl-1695e"
Environmental Science and Technology 42 ISSN 0013-936X; ESTHAG FT
Wan, Jiamin; Herman, Don; Kim, Yongman; Hazen, Terry C.; Tokunaga, Tetsu K.; Firestone, Mary K.; Daly, Rebecca A.; Brodie, Eoin L.
Earth Sciences Division - Funding Information:
- DE-AC02-05CH11231
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