Journal
JOURNAL OF CONTAMINANT HYDROLOGY
Volume 58, Issue 1-2, Pages 1-12Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/S0169-7722(02)00032-3
Keywords
uranium; colloid transport; humic substances; column experiments; breakthrough curve; kinetics
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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 At/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-bome 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. (C) 2002 Published by Elsevier Science B.V.
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