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Role of Naturally Occurring Organic Matter on Thorium Transport in a Wetland

Published online by Cambridge University Press:  11 February 2011

Daniel I. Kaplan  and
A. S. Knox
Daniel I. Kaplan
Affiliation:
Westinghouse Savannah River Company, Aiken, SC 29808, U.S.A.
A. S. Knox
Affiliation:
Westinghouse Savannah River Company, Aiken, SC 29808, U.S.A.
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Abstract

A wetland located on the Savannah River Site in Aiken, South Carolina has become contaminated by a number of radionuclides as a result of operating a pilot-scale nuclear test facility. Sediment Th-232 concentration at the site exceed 700 mg/kg, whereas background concentrations are ∼7 mg/kg. The Th is relatively mobile, having moved >300-m since 1958 and greatly exceeding contaminant transport model predictions. Studies were initiated to determine the chemical cause for the enhanced transport of Th. Particle-size fractionation studies showed that colloids alone were not likely responsible for all of the enhanced transport of Th. Sediment sequential extraction data showed that >80% of the Th was associated with the sediment organic fraction. In an experiment in which varying soil amendments resulted in the release of dissolved organic carbon (DOC) to the aqueous phase, a significant correlation (r = 0.91; p ≤ 0.01, n = 8) was calculated between aqueous Th and DOC. Pore water Th partitioning to hydrophobic resins suggested that 33% of the aqueous Th was associated with organic matter. Together, these results provide indirect evidence support the notion that enhanced mobility of Th at the site may in part be due to the presence of Th-DOC complexes.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 757: Symposium II – Scientific Basis for Nuclear Waste Management XXVI , 2002 , II7.2
Copyright
Copyright © Materials Research Society 2003

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