title: No measurable changes in (238)U/(235)U due to desorption-adsorption of U(VI) from groundwater at the Rifle, Colorado, integrated field research challenge site.
abstract: Groundwater samples were collected from the Integrated Field Research Challenge field site in Rifle, Colorado, over the course of a bicarbonate-induced U desorption-adsorption experiment. Uranium concentrations and high precision U isotopic compositions ((238)U/(235)U) of these groundwater samples were determined and used to assess the impact of bicarbonate-induced U(VI) desorption from contaminated sediments on the (238)U/(235)U of groundwater. The (238)U/(235)U of groundwater was not significantly impacted by bicarbonate-induced desorption of U(VI) from mineral surfaces or by adsorption of advecting U(VI) from upgradient locations onto those surfaces after the treatment. Assuming this absence of a significant shift in U isotopic composition associated with desorption-adsorption applies to other systems, reduction of U(VI) to U(IV) is expected to be the dominant source of U isotopic fractionation associated with removal of U(VI) from pore water as a result of natural and stimulated reductive pathways. Thus, changes in the (238)U/(235)U composition of uranium-bearing fluids should be useful in quantifying the extent of reduction.
authors: Department of Geology, University of Illinois at Urbana-Champaign , 208 Natural History Building, 1301 West Green Street, Urbana, Illinois 61801, USA. ashiel@illinois.edu
authors: Alyssa E
authors: AE
authors: Shiel
authors: Parker G
authors: PG
authors: Laubach
authors: Thomas M
authors: TM
authors: Johnson
authors: Craig C
authors: CC
authors: Lundstrom
authors: Philip E
authors: PE
authors: Long
authors: Kenneth H
authors: KH
authors: Williams
mesh_terms: D000327:Adsorption; D001639:Bicarbonates / Q000737:chemistry*; D003120:Colorado; D019015:Geologic Sediments / Q000032:analysis*; D060587:Groundwater / Q000032:analysis*; D014501:Uranium / Q000032:analysis*; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D001639:Bicarbonates; D014875:Water Pollutants, Radioactive; D014501:Uranium