Evidence for Multiple Modes of Uranium Immobilization by an Anaerobic Bacterium

Journal Article · Sun May 01 00:00:00 EDT 2011 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/j.gca.2011.02.040· OSTI ID:1012674

Ray, Allison E; Bargar, John R; Dohnalkova, Alice C; Sivaswamy, Vaidee; Fujita, Yoshiko; Magnuson, Timothy S

ABSTRACT Microbial reduction of hexavalent uranium has been studied widely for its potential role in bioremediation and removal of soluble U(VI) from contaminated groundwater. More recently, some microorganisms have been examined for their role in immobilization of U(VI) via precipitation of uranyl phosphate minerals mediated by microbial phosphate release, alleviating the requirement for long-term redox control. Here, we investigated the mechanism of U(VI) removal mediated by an environmental isolate, strain UFO1, that is indigenous to the Field Research Center (FRC) in Oak Ridge, TN and has been detected in U(VI)-contaminated sediments. U(VI) removal was examined in the presence and absence of the electron-shuttling moiety, anthraquinone-2,6-disulfonate (AQDS). Cell suspensions were capable of the near complete removal of 100 uM U(VI) from solution within 48 hours; U(VI) removal was not dependent on the presence of an exogenous electron donor or AQDS, although AQDS increased the rate of U(VI) removal. Profiles of ortho-phosphate concentration over time suggested phosphate liberation from cells. However, X-ray Absorption Near Edge Structure (XANES) spectroscopic measurements indicated that U(IV) was the predominant oxidation state of uranium in cell suspensions in both the absence and presence of 100 uM AQDS. Extended X-ray Absorption Fine Structure spectroscopy (EXAFS) measurements indicated that 20% of the cell-associated precipitates in a U(VI)-treated suspension that lacked AQDS had spectral characteristics consistent with a uranyl phosphate solid phase. EXAFS fits further show that that U(IV) is present dominantly as a monomeric sorbed complex. TEM-EDS confirmed the presence of uranyl phosphate with a U:P ratio consistent with autunite (1:1). These results suggest that strain UFO1 has the ability to mediate U(VI) removal from solution via both reductive and phosphate precipitation mechanisms, and may potentially be useful for the remediation of U-contaminated sediments at the FRC.

• Research Organization: Idaho National Lab. (INL), Idaho Falls, ID (United States)
• Sponsoring Organization: OTHER
• DOE Contract Number: DE-AC07-05ID14517
• OSTI ID: 1012674
• Report Number(s): INL/JOU-08-14289; GCACAK; TRN: US201110%%281
• Journal Information: Geochimica et Cosmochimica Acta, Vol. 75, Issue 10; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES/GLOBAL CLIMATE CHANGE STUDIES AND CLIMATE MITIGATION
ABSORPTION
AUTUNITE
BINDING ENERGY
BIOREMEDIATION
ELECTRONS
FINE STRUCTURE
MICROORGANISMS
PHOSPHATES
PRECIPITATION
REMOVAL
SEDIMENTS
SPECTROSCOPY
STRAINS
URANIUM
URANYL PHOSPHATES
VALENCE
bioremediation
U(VI) reduction
uranyl phosphate