title: Oxidation state and local structure of plutonium reacted with magnetite, mackinawite, and chukanovite.
abstract: Due to their redox reactivity, surface sorption characteristics, and ubiquity as corrosion products or as minerals in natural sediments, iron(II)-bearing minerals control to a large extent the environmental fate of actinides. Pu-L(III)-edge XANES and EXAFS spectra were used to investigate reaction products of aqueous (242)Pu(III) and (242)Pu(V) reacted with magnetite, mackinawite, and chukanovite under anoxic conditions. As Pu concentrations in the liquid phase were rapidly below detection limit, oxidation state and local structure of Pu were determined for Pu associated with the solid mineral phase. Pu(V) was reduced in the presence of all three minerals. A newly identified, highly specific Pu(III)-sorption complex formed with magnetite. Solid PuO(2) phases formed in the presence of mackinawite and chukanovite; in the case of chukanovite, up to one-third of plutonium was also present as Pu(III). This highlights the necessity to consider, under reducing anoxic conditions, Pu(III) species in addition to tetravalent PuO(2) for environmental risk assessment. Our results also demonstrate the necessity to support thermodynamic calculations with spectroscopic data.
authors.affiliation: Institut für Radiochemie, Helmholtz Zentrum Dresden Rossendorf, Postfach 510119, 01314 Dresden, Germany. kirsch@esrf.fr
authors.forename: Regina
authors.initials: R
authors.lastname: Kirsch
authors.forename: David
authors.initials: D
authors.lastname: Fellhauer
authors.forename: Marcus
authors.initials: M
authors.lastname: Altmaier
authors.forename: Volker
authors.initials: V
authors.lastname: Neck
authors.forename: Andre
authors.initials: A
authors.lastname: Rossberg
authors.forename: Thomas
authors.initials: T
authors.lastname: Fanghänel
authors.forename: Laurent
authors.initials: L
authors.lastname: Charlet
authors.forename: Andreas C
authors.initials: AC
authors.lastname: Scheinost
mesh_terms: D000327:Adsorption; D005290:Ferric Compounds / Q000737:chemistry*; D052203:Ferrosoferric Oxide / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D011005:Plutonium / Q000737:chemistry*; D011848:Radioactive Pollutants / Q000737:chemistry*; D013816:Thermodynamics; D056928:X-Ray Absorption Spectroscopy / Q000379:methods
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D011848:Radioactive Pollutants; D011005:Plutonium; D052203:Ferrosoferric Oxide