Surface Area and Radionuclide Sorption in Contaminated Aquifers

Abstract

Abstract Strong linear correlations between 90Sr and 60Co sorption and BET surface area have been found in samples of sands from three contaminated aquifers. The sands have a granitic mineralogy, and the sequence for both surface area and radionuclide retention is vermiculite >> sericite > amphibole > muscovite = biotite > feldspar > quartz. Where aqueous geochemistry of the aquifer is relatively constant, a strong linear correlation between whole-sediment surface area and in situ radionuclide distribution coefficients was found. Distribution coefficients cannot be reliably predicted from surface area measurements if substantial differences in major ion chemistry are known or suspected at the various soil sampling localities. From the results presented here, we conclude that surface coatings (predominantly iron oxyhydroxides) provide most of the surface area and sorption capacity. Particle mineralogy has a major influence on the development of coatings, but plays a minor role in the direct sorption of contaminants.