title: Hexavalent uranium diffusion into soils from concentrated acidic and alkaline solutions.
abstract: Uranium contamination of soils and sediments often originates from acidic or alkaline waste sources, with diffusion being a major transport mechanism. Measurements of U(VI) diffusion from initially pH 2 and pH 11 solutions into a slightly alkaline Altamont soil and a neutral Oak Ridge soil were obtained through monitoring uptake from boundary reservoirs and from U concentration profiles within soil columns. The soils provided pH buffering, resulting in diffusion at nearly constant pH. Micro X-ray absorption near edge structure spectra confirmed that U remained in U(VI) forms in all soils. Time trends of U(VI) depletion from reservoirs and U(VI) concentration profiles within soil columns yielded Kdvalues consistent with those determined in batch tests at similar concentrations (approximately 1 mM) and much lower than values for sorption at much lower concentrations (nM to microM). These results show that U(VI) transport at high concentrations can be relatively fast at non-neutral pH, with negligible surface diffusion, because of weak sorption.
authors.affiliation: Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA. tktokunaga@lbl.gov
authors.forename: Tetsu K
authors.initials: TK
authors.lastname: Tokunaga
authors.forename: Jiamin
authors.initials: J
authors.lastname: Wan
authors.forename: Jasquelin
authors.initials: J
authors.lastname: Pena
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Sutton
authors.forename: Matthew
authors.initials: M
authors.lastname: Newville
mesh_terms: D000327:Adsorption; D004058:Diffusion; D004784:Environmental Monitoring; D006863:Hydrogen-Ion Concentration; D012990:Soil Pollutants, Radioactive / Q000032:analysis*; D013057:Spectrum Analysis; D014501:Uranium / Q000032:analysis / Q000737:chemistry*
chemical_list: D012990:Soil Pollutants, Radioactive; D014501:Uranium