Humic colloid-borne migration of uranium in sand columns.
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.
Artinger
R
R
Forschungszentrum Karlsruhe, Institut für Nukleare Entsorgung, Germany. artinger@ine.fzk.de
Rabung
T
T
Kim
J I
JI
Sachs
S
S
Schmeide
K
K
Heise
K H
KH
Bernhard
G
G
Nitsche
H
H
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
D003102:Colloids; D006812:Humic Substances; D014875:Water Pollutants, Radioactive; D014501:Uranium; D012822:Silicon Dioxide