title: Long-term in situ oxidation of biogenic uraninite in an alluvial aquifer: impact of dissolved oxygen and calcium.
abstract: Oxidative dissolution controls uranium release to (sub)oxic pore waters from biogenic uraninite produced by natural or engineered processes, such as bioremediation. Laboratory studies show that uraninite dissolution is profoundly influenced by dissolved oxygen (DO), carbonate, and solutes such as Ca(2+). In complex and heterogeneous subsurface environments, the concentrations of these solutes vary in time and space. Knowledge of dissolution processes and kinetics occurring over the long-term under such conditions is needed to predict subsurface uranium behavior and optimize the selection and performance of uraninite-based remediation technologies over multiyear periods. We have assessed dissolution of biogenic uraninite deployed in wells at the Rifle, CO, DOE research site over a 22 month period. Uraninite loss rates were highly sensitive to DO, with near-complete loss at >0.6 mg/L over this period but no measurable loss at lower DO. We conclude that uraninite can be stable over decadal time scales in aquifers under low DO conditions. U(VI) solid products were absent over a wide range of DO values, suggesting that dissolution proceeded through complexation and removal of oxidized surface uranium atoms by carbonate. Moreover, under the groundwater conditions present, Ca(2+) binds strongly to uraninite surfaces at structural uranium sites, impacting uranium fate.
authors.affiliation: †Stanford Synchrotron Radiation Lightsource, SLAC, 2575 Sand Hill Road, Menlo Park, California 94025, United States.
authors.forename: Juan S
authors.initials: JS
authors.lastname: Lezama-Pacheco
authors.affiliation: §Department of Energy, Environmental, and Chemical Engineering, Washington University, One Brookings Drive, Saint Louis, Missouri 63130, United States.
authors.forename: José M
authors.initials: JM
authors.lastname: Cerrato
authors.affiliation: ‡Environmental Microbiology Laboratory, École Polytechnique Fédérale de Lausanne, Lausanne, CH 1015, Switzerland.
authors.forename: Harish
authors.initials: H
authors.lastname: Veeramani
authors.affiliation: ‡Environmental Microbiology Laboratory, École Polytechnique Fédérale de Lausanne, Lausanne, CH 1015, Switzerland.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Alessi
authors.affiliation: ‡Environmental Microbiology Laboratory, École Polytechnique Fédérale de Lausanne, Lausanne, CH 1015, Switzerland.
authors.forename: Elena
authors.initials: E
authors.lastname: Suvorova
authors.affiliation: ‡Environmental Microbiology Laboratory, École Polytechnique Fédérale de Lausanne, Lausanne, CH 1015, Switzerland.
authors.forename: Rizlan
authors.initials: R
authors.lastname: Bernier-Latmani
authors.affiliation: §Department of Energy, Environmental, and Chemical Engineering, Washington University, One Brookings Drive, Saint Louis, Missouri 63130, United States.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Giammar
authors.affiliation: ∥Earth Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Philip E
authors.initials: PE
authors.lastname: Long
authors.affiliation: ∥Earth Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Williams
authors.affiliation: †Stanford Synchrotron Radiation Lightsource, SLAC, 2575 Sand Hill Road, Menlo Park, California 94025, United States.
authors.forename: John R
authors.initials: JR
authors.lastname: Bargar
mesh_terms: D001673:Biodegradation, Environmental; D002118:Calcium / Q000737:chemistry*; D002254:Carbonates / Q000737:chemistry; D005583:Fourier Analysis; D060587:Groundwater / Q000737:chemistry*; D007700:Kinetics; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D012995:Solubility; D014501:Uranium / Q000737:chemistry*; D014875:Water Pollutants, Radioactive / Q000032:analysis; D056928:X-Ray Absorption Spectroscopy
chemical_list: D002254:Carbonates; D014875:Water Pollutants, Radioactive; D014501:Uranium; D010100:Oxygen; D002118:Calcium