title: Beam-induced oxidation of monomeric U(IV) species.
abstract: Uranium L(III)-edge X-ray absorption spectroscopy is often used to probe the oxidation state and coordination of uranium in environmental samples, and micrometre-sized beams can be used to spatially map the distribution of uranium relative to other elements. Here a variety of uranium-containing environmental samples are analyzed at both microbeam and larger beam sizes to determine whether reoxidation of U(IV) occurred. Monomeric U(IV), a recently discovered product of U(VI) reduction by microbes and certain iron-bearing minerals at uranium-contaminated field sites, was found to be reoxidized during microbeam (3 µm × 2 µm) analysis of biomass and sediments containing the species but not at larger beam sizes. Thus, care must be taken when using X-ray microprobes to analyze samples containing monomeric U(IV).
authors.affiliation: Environmental Microbiology Laboratory, Ecole Polytechnique, Fédérale de Lausanne, Switzerland. daniel.alessi@epfl.ch
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Alessi
authors.forename: Benjamin
authors.initials: B
authors.lastname: Uster
authors.forename: Camelia N
authors.initials: CN
authors.lastname: Borca
authors.forename: Daniel
authors.initials: D
authors.lastname: Grolimund
authors.forename: Rizlan
authors.initials: R
authors.lastname: Bernier-Latmani
mesh_terms: D001673:Biodegradation, Environmental; D018533:Biomass; D019015:Geologic Sediments / Q000737:chemistry; D010084:Oxidation-Reduction; D020592:Shewanella / Q000378:metabolism; D014501:Uranium / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D014501:Uranium