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Soil Sci. Soc. Am. J
Vol. 69, No. xx, 2005; Pages: 1652–1657


Rhizosphere Effects on Cesium Fixation Sites of Soil Containing Micaceous Clays

Laura A. Wendling,* James B. Harsh, Carl D. Palmer, Melinda A. Hamilton, Heather M. Dion, Jeffrey S. Boyle, and Markus Flury

USDA-ARS, P.O. Box 646120, Washington StateUniv., Pullman,WA 99164-6120.

Abstract

Physical and chemical weathering processes in the rhizosphere maylead to the generation of a greater density of Cs-selective frayed edge sites (FES) on rhizosphere soil as compared with bulk soil. This studywas undertaken to determine if there are significant differences between bulk and rhizosphere soils from the Idaho National Laboratory(INL) with respect to their ability to bind Cs. The capacity of FESon bulk and rhizosphere soil materials and conditional Cs/K selectivityof FES (cKexFES) were determined as a function of both soil type and initial exchanger composition. The FES capacity was significantlyhigher in untreated, Ca-saturated, and K-saturated rhizosphere soilmaterials as compared with bulk soil materials. Sorption–desorptionisotherms were obtained at Cs concentrations between 5 x10-9 and5 x10-6 M. No difference in Cs sorption was observed between bulkand rhizosphere soil materials. The composition of the exchangingsolution had the greatest effect on the magnitude of Cs desorption;significantly more Cs was desorbed in the presence of KCl than ineither CaCl2 or a mixed-cation soil solution. In addition, Cs desorptionwas greater from rhizosphere soil materials relative to bulk soil materials. Cesium selectivity with respect to both Ca and K was significantlysuppressed by weathering in the rhizosphere. We conclude that enhanced weathering in the rhizosphere increased the Cs sorption capacity of FES, but also reduced Cs selectivity on these sites. EnhancedCs desorption from rhizosphere INL soils is likely in the presence ofactively growing plants and associated microorganisms.

Keywords:frayed edgesites;rhizosphere soil;Micaceous Clays;microorganisms;phyllosilicate minerals;spectrophotometry;radionuclides.


Corresponding author:

E-mail: lawendling@wsu.edu

 

 
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