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Title: Influence of Uranium Concentration and pH on U-Phosphate Biomineralization by Caulobacter OR37

Journal Article · · Environmental Science and Technology

Uranium contamination of soils and groundwater in the United States represents a significant health risk and will require multiple remediation approaches. Microbial phosphatase activity coupled to the addition of an organic P source has recently been studied as a remediation strategy that provides an extended release of inorganic P (Pi) into U-contaminated sites, resulting in the precipitation of meta-autunite minerals. Previous laboratory- and field-based biomineralization studies have investigated environments with relatively high U concentrations (>20 μM). However, most contaminated sites have much lower U concentrations (<2 μM). The Environmental Protection Agency (EPA) limit for U in drinking water is 0.126 μM. Reaching this regulatory limit becomes challenging as U concentrations approach autunite solubility. Furthermore, we studied the precipitation of U(VI)-phosphate minerals by an environmental isolate of Caulobacter sp. (strain OR37) from an Oak Ridge, Tennessee, U-contaminated site. Abiotic U(VI) solubility experiments reveal that U(VI)-phosphate minerals do not form in the presence of excess Pi (500 μM) when U(VI) concentrations are <1 μM and pH is <5. When OR37 cells are reacted under the same conditions with Pi or glycerol-2-phosphate, U(VI)-phosphate mineral formation was observed, along with the formation of intracellular polyphosphate granules. These results show that bacteria provide supersaturated microenvironments needed for U(VI)-phosphate mineralization while hydrolyzing organic P sources. This provides a pathway to lower U concentrations to below EPA limits for drinking water.

Research Organization:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Biological and Environmental Research (BER)
Grant/Contract Number:
AC52-07NA27344
OSTI ID:
1787219
Report Number(s):
LLNL-JRNL-813614; 1021681; TRN: US2210425
Journal Information:
Environmental Science and Technology, Vol. 55, Issue 3; ISSN 0013-936X
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

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