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Modelling uranium leaching from agricultural soils to groundwater as a criterion for comparison with complementary safety indicators

Published online by Cambridge University Press:  21 March 2011

D. Jacques ,
J. Šimůnek ,
D. Mallants  and
M.Th. van Genuchten
D. Jacques
Affiliation:
Waste and Disposal Department, SCK•CEN, Boeretang 200, B-2400 Mol, Belgium
J. Šimůnek
Affiliation:
University of California Riverside, Riverside, CA 92521, USA
D. Mallants
Affiliation:
Waste and Disposal Department, SCK•CEN, Boeretang 200, B-2400 Mol, Belgium
M.Th. van Genuchten
Affiliation:
George E. Brown, Jr. Salinity Laboratory, 450 W Big Springs RD, Riverside, CA 92507, USA
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Abstract

Naturally occurring radionuclides can also end up in soils and groundwater due to human practices, such as application of certain fertilizers in agriculture. Many mineral fertilizers, particularly (super)phosphates, contain small amounts of 238U and 230Th which eventually may be leached from agricultural soils to underlying water resources. Field soils that receive P-fertilizers accumulate U and Th and their daughter nuclides, which eventually may leach to groundwater. Our objective was to numerically assess U migration in soils. Calculations were based on a new reactive transport model, HP1, which accounts for interactions between U and organic matter, phosphate, and carbonate. Solid phase interactions were simulated using a surface complexation module. Furthermore, all geochemical processes were coupled with a model accounting for dynamic changes in the soil water content and the water flux. The capabilities of the code in calculating natural U fluxes to groundwater were illustrated using a semi-synthetic 200-year long time series of climatological data for Belgium. Based on an average fertilizer application, the input of phosphate and uranium in the soil was defined. This paper discusses calculated U distributions in the soil profile as well as calculated U fluxes leached from a 100-cm deep soil profile. The calculated long-term leaching rates originating from fertilization are significantly higher after 200 years than estimated release rates from lowlevel nuclear waste repositories.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 932: Symposium – Scientific Basis for Nuclear Waste Management XXIX , 2006 , 2.1
Copyright
Copyright © Materials Research Society 2006

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