Simulation of reactive transport of uranium(VI) in groundwater with variable chemical conditions

The reactive transport of U(VI) in a shallow alluvial aquifer beneath a former U(VI) mill located near Naturita, CO, was simulated using a surface complexation model (SCM) to describe U(VI) adsorption. The groundwater had variable U(VI) concentrations (0.01-20 micromolar), variable alkalinity (2.5-1...

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Bibliographic Details
Published in:Water resources research 2006-04, Vol.42 (4), p.n/a
Main Authors: Curtis, G.P, Davis, J.A, Naftz, D.L
Format: Article
Language:English
Subjects:
adsorption
aquifers
geochemistry
groundwater contamination
groundwater flow
groundwater recharge
hydraulic conductivity
hydrogeology
mine spoil
reactive transport
sediment transport
simulation models
solute transport
uranium
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Summary:The reactive transport of U(VI) in a shallow alluvial aquifer beneath a former U(VI) mill located near Naturita, CO, was simulated using a surface complexation model (SCM) to describe U(VI) adsorption. The groundwater had variable U(VI) concentrations (0.01-20 micromolar), variable alkalinity (2.5-18 meq/L), and a nearly constant pH equal to 7.1. U(VI) K(D) values decreased with increasing U(VI) and alkalinity, and these parameters were more important than sediment variability in controlling K(D) values. Reactive transport simulations were fit to the observed U(VI) and alkalinity by varying the concentration of U(VI) and alkalinity in recharge at the source area. Simulated K(D) values varied temporally and spatially because of the differential transport of U(VI) and alkalinity and the nonlinearity of U(VI) adsorption. The model also simulated the observed U(VI) tailing, which would not be expected from a constant K(D) model. The simulated U(VI) concentrations were sensitive to the recharge flux because of the increased flux of U(VI) to the aquifer. The geochemical behavior of U(VI) was most sensitive to the alkalinity and was relatively insensitive to pH.
ISSN:0043-1397
1944-7973
DOI:10.1029/2005WR003979