Title:
Nonreductive biomineralization of uranium(VI) as a result of microbial phosphatase activity

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dc.contributor.advisor Taillefert, Martial
dc.contributor.author Beazley, Melanie J. en_US
dc.contributor.committeeMember DiChristina, Thomas
dc.contributor.committeeMember Sobecky, Patricia
dc.contributor.committeeMember Van Cappellen, Philippe
dc.contributor.committeeMember Webb, Samuel
dc.contributor.department Earth and Atmospheric Sciences en_US
dc.date.accessioned 2009-08-26T17:34:53Z
dc.date.available 2009-08-26T17:34:53Z
dc.date.issued 2009-07-06 en_US
dc.description.abstract Uranium contamination of soils and groundwater at Department of Energy facilities across the United States is a primary environmental concern and the development of effective remediation strategies is a major challenge. Bioremediation, or the use of microbial enzymatic activity to facilitate the remediation of a contaminant, offers a promising in situ approach that may be less invasive than traditional methods, such as pump and treat or excavation. This study demonstrates for the first time the successful biomineralization of uranium phosphate minerals as a result of microbial phosphatase activity at low pH in both aerobic and anaerobic conditions using pure cultures and soils from a contaminated waste site. Pure cultures of microorganisms isolated from soils of a low pH, high uranium- and nitrate-contaminated waste site, expressed constitutive phosphatase activity in response to an organophosphate addition in aerobic and anaerobic incubations. Sufficient phosphate was hydrolyzed to precipitate 73 to 95% total uranium as chernikovite identified by synchrotron X-ray absorption spectroscopy and X-ray diffraction. Highest rates of uranium precipitation and phosphatase activity were observed between pH 5.0 and 7.0. Indigenous microorganisms were also stimulated by organophosphate amendment in soils from a contaminated waste site using flow-through reactors. High phosphate concentrations (0.5 to 3 mmol L-1) in pore water effluents were observed within days of organophosphate addition. Highest rates of phosphatase activity occurred at pH 5.5 in naturally low pH soils in the presence of high uranium and nitrate concentrations. The precipitation of uranium phosphate was identified by a combination of pore water measurements, solid phase extractions, synchrotron-based X-ray spectroscopy, and a reactive transport model. The results of this study demonstrate that uranium is biomineralized to a highly insoluble uranyl phosphate mineral as a result of enzymatic hydrolysis of an organophosphate compound over a wide range of pH, in both aerobic and anaerobic conditions, and in the presence of high uranium and nitrate concentrations. The nonreductive biomineralization of U(VI) provides a promising new approach for in situ uranium bioremediation in low pH, high nitrate, and aerobic conditions that could be complementary to U(VI) bioreduction in high pH, low nitrate, and reducing environments. en_US
dc.description.degree Ph.D. en_US
dc.identifier.uri http://hdl.handle.net/1853/29644
dc.publisher Georgia Institute of Technology en_US
dc.subject Phosphatase en_US
dc.subject Bioremediation en_US
dc.subject Uranium biomineralization en_US
dc.subject Biogeochemistry en_US
dc.subject.lcsh Biomineralization
dc.subject.lcsh Uranium
dc.subject.lcsh In situ remediation
dc.subject.lcsh Radioactive wastes Biodegradation
dc.subject.lcsh Phosphatases
dc.title Nonreductive biomineralization of uranium(VI) as a result of microbial phosphatase activity en_US
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.advisor Taillefert, Martial
local.contributor.corporatename School of Earth and Atmospheric Sciences
local.contributor.corporatename College of Sciences
relation.isAdvisorOfPublication 3837e5f7-5f3d-454d-af34-f011540de5f8
relation.isOrgUnitOfPublication b3e45057-a6e8-4c24-aaaa-fb00c911603e
relation.isOrgUnitOfPublication 85042be6-2d68-4e07-b384-e1f908fae48a
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