title: Microanalysis (micro-XRF, micro-XANES, and micro-XRD) of a tertiary sediment using microfocused synchrotron radiation.
abstract: Micro-focused synchrotron radiation techniques to investigate actinide elements in geological samples are becoming an increasingly used tool in nuclear waste disposal research. In this article, results using mu-focus techniques are presented from a bore core section of a U-rich tertiary sediment collected from Ruprechtov, Czech Republic, a natural analog to nuclear waste repository scenarios in deep geological formations. Different methods are applied to obtain various, complementary information. Elemental and element chemical state distributions are obtained from micro-XRF measurements, oxidation states of As determined from micro-XANES, and the crystalline structure of selected regions are studied by means of micro-XRD. We find that preparation of the thin section created an As oxidation state artifact; it apparently changed the As valence in some regions of the sample. Results support our previously proposed hypothesis of the mechanism for U-enrichment in the sediment. AsFeS coating on framboid Fe nodules in the sediment reduced mobile groundwater-dissolved U(VI) to less-soluble U(IV), thereby immobilizing the uranium in the sediment.
authors.affiliation: Forschungszentrum Karlsruhe, Institut für Nukleare Entsorgung, D-76021 Karlsruhe, Germany. melissa@ine.fzk.de
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Denecke
authors.forename: Andrea
authors.initials: A
authors.lastname: Somogyi
authors.forename: Koen
authors.initials: K
authors.lastname: Janssens
authors.forename: Rolf
authors.initials: R
authors.lastname: Simon
authors.forename: Kathy
authors.initials: K
authors.lastname: Dardenne
authors.forename: Ulrich
authors.initials: U
authors.lastname: Noseck