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Simulation of reactive transport of uranium(VI) in groundwater with variable chemical conditions
Author(s) -
Curtis Gary P.,
Davis James A.,
Naftz David L.
Publication year - 2006
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2005wr003979
Subject(s) - alkalinity , groundwater , aquifer , groundwater recharge , flux (metallurgy) , chemistry , hydrology (agriculture) , environmental chemistry , adsorption , environmental science , geology , geotechnical engineering , organic chemistry
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 μM), 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.