In environments characterized by low pH and/or high nitrate, the biomineralization of U(VI)-phosphate minerals represents a uniquely suited bioremediation method involving microbially-mediated hydrolysis of organophosphates coupled to a chemical precipitation of sparingly soluble U(VI)-phosphate minerals. In this study, the ability of natural microbial phytases to hydrolyze phytate, a naturally-occurring and abundant organophosphate, and precipitate uranium-phosphate minerals was investigated through a combination of sediment microcosms, soil slurries, and pure culture studies. In this study, biomineralization of U(VI)-phosphate minerals promoted by addition of glycerol-2-phosphate was shown to outcompete bioreduction in anaerobically-maintained sediment microcosms containing contaminated soils. Addition of phytate to aerobic soils slurries containing ORFRC soils also resulted in significant production of inorganic phosphate, and two microorganisms that efficiently hydrolyze phytate were isolated from these experiments. Overall, the results of this study demonstrate phytate hydrolysis by subsurface microorganisms coupled to precipitation of U(VI)-phosphate minerals for the first time, suggesting that phytate may represent an ideal organophosphate to promote this process.

The behavior of U in near surface sedimentary environments has changed throughout geologic time. There is a marked shift in U (IV) mineral stability and deposit style at approximately 2200 Ma due to changes in the concentration of O in the atmosphere. For example, prior to 2200 Ma, fluvial U deposits could form and U(IV) were stable in surface and near-surface environments. In modern, anthropogenic sedimentary systems such as U tailings, U (IV) minerals are not stable and readily oxidize to U (VI) minerals. In addition, U is much more mobile in modern sediments relative sediments that were deposited prior to 2200 Ma.

75 leaves : graphs ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1980) from the Dept. of Physical and Inorganic Chemistry, University of Adelaide

Thesis (Ph.D. 1980) from the Department of Physical and Inorganic Chemistry, University of Adelaide.

Thèse 3e cycle--Géologie--Nantes, 1983. / Bibliogr. p. 137-143. Résumés en français et en anglais.

Th. 3e cycle--Sci. des matériaux--Nancy 1, 1983. / Bibliogr. p. 219-225.

Thesis (M.S.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains ix, 85 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 71-74).

Thesis (PhD)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: Brent M. Peyton. Includes bibliographical references.

Thesis (Ph. D.)--University of Chicago.

Thesis (Ph. D.)--University of Chicago.