Long-Term Selective Retention of Natural Cs and Rb by Highly Weathered Coastal Plain Soils

Naturally occurring Cs and Rb are distinctly more abundant relative to K in the highly weathered upland soils of the Savannah River Site, South Carolina, than in average rock of Earth’s upper continental crust (UCC), by factors of 10 and 4, respectively. Naturally occurring Cs has been selectively r...

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Bibliographic Details
Published in:Environmental science & technology 2012-04, Vol.46 (7), p.3837-3843
Main Authors: Wampler, J. M, Krogstad, Eirik J, Elliott, W. Crawford, Kahn, Bernd, Kaplan, Daniel I
Format: Article
Language:English
Subjects:
Aluminum Silicates - chemistry
Cesium - analysis
Chemical Fractionation
Earth sciences
Earth, ocean, space
Ecosystem
Engineering and environment geology. Geothermics
Evolution
Exact sciences and technology
Geochemistry
Ion exchange
Particle Size
Pollution, environment geology
Potassium - analysis
Rubidium - analysis
Seawater - chemistry
Soil - chemistry
Soil and rock geochemistry
Soil contaminants
Soil Pollutants - analysis
Soils
South Carolina
Surficial geology
Time Factors
Weather
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Summary:Naturally occurring Cs and Rb are distinctly more abundant relative to K in the highly weathered upland soils of the Savannah River Site, South Carolina, than in average rock of Earth’s upper continental crust (UCC), by factors of 10 and 4, respectively. Naturally occurring Cs has been selectively retained during soil evolution, and Rb to a lesser extent, while K has been leached away. In acid extracts of the soils, the Cs/K ratio is about 50 times and the Rb/K ratio about 15 times the corresponding ratios for the UCC, indicating that relatively large amounts of natural Cs and Rb have been sequestered in soil microenvironments that are highly selective for these elements relative to K. Cation exchange favoring Cs and Rb ions, and subsequent fixation of the ions, at sites in interlayer wedge zones within hydroxy-interlayered vermiculite particles may account for the observations. The amounts of stable Cs retained and the inferred duration of the soil evolution, many thousands of years, provide new insights regarding long-term stewardship of radiocesium in waste repositories and contaminated environments. Study of natural Cs in soil adds a long-term perspective on Cs transport in soils not available from studies of radiocesium.
ISSN:0013-936X
1520-5851
DOI:10.1021/es2035834