title: Humic colloid-borne migration of uranium in sand columns.
abstract: Column experiments were carried out to investigate the influence of humic colloids on subsurface uranium migration. The columns were packed with well-characterized aeolian quartz sand and equilibrated with groundwater rich in humic colloids (dissolved organic carbon (DOC): 30 mg dm(-3)). U migration was studied under an Ar/1% CO2 gas atmosphere as a function of the migration time, which was controlled by the flow velocity or the column length. In addition, the contact time of U with groundwater prior to introduction into a column was varied. U(VI) was found to be the dominant oxidation state in the spiked groundwater. The breakthrough curves indicate that U was transported as a humic colloid-borne species with a velocity up to 5% faster than the mean groundwater flow. The fraction of humic colloid-borne species increases with increasing prior contact time and also with decreasing migration time. The migration behavior was attributed to a kinetically controlled association/dissociation of U onto and from humic colloids and also a subsequent sorption of U onto the sediment surface. The column experiments provide an insight into humic colloid-mediated U migration in subsurface aquifers.
authors.affiliation: Forschungszentrum Karlsruhe, Institut für Nukleare Entsorgung, Germany. artinger@ine.fzk.de
authors.forename: R
authors.initials: R
authors.lastname: Artinger
authors.forename: T
authors.initials: T
authors.lastname: Rabung
authors.forename: J I
authors.initials: JI
authors.lastname: Kim
authors.forename: S
authors.initials: S
authors.lastname: Sachs
authors.forename: K
authors.initials: K
authors.lastname: Schmeide
authors.forename: K H
authors.initials: KH
authors.lastname: Heise
authors.forename: G
authors.initials: G
authors.lastname: Bernhard
authors.forename: H
authors.initials: H
authors.lastname: Nitsche
mesh_terms: D000327:Adsorption; D002845:Chromatography; D003102:Colloids / Q000737:chemistry; D006801:Humans; D006812:Humic Substances / Q000737:chemistry; D012822:Silicon Dioxide; D014501:Uranium / Q000737:chemistry*; D014875:Water Pollutants, Radioactive; D018508:Water Purification
chemical_list: D003102:Colloids; D006812:Humic Substances; D014875:Water Pollutants, Radioactive; D014501:Uranium; D012822:Silicon Dioxide