A STUDY ON RADIONUCLIDE ASSOCIATION WITH SOIL COMPONENTS USING A SEQUENTIAL EXTRACTION PROCEDURE

Measurements performed in 1986-1988 demonstrate that most of the radiocesium isotopes (137Cs and134Cs) deposited after the Chernobyl accident are still located in the upper soil layers (0-2 cm). The vertical migration appears to be slow, and only a small fraction of the radiocesium has been transferred into the biological cycle. Sequential extraction techniques have been utilized in order to investigate the degree of binding or association between deposited radionuclides (137Cs,134Cs and90Sr) and components in soil. The results indicate that a major fraction of the radiocesium is associated strongly with organic and mineral materials in the litter or upper soil layers: less than 10% is easily leachable. The distribution of137Cs throughout the fractions was similar to that determined for naturally occurring stable cesium (133Cs), implying that isotopic exchange had been extensive. For90Sr, the results show a relatively high leachable fraction. Therefore, present results indicate that radiocesium should be less mobile, and less available for root uptake, than90Sr in soil. © 1990 Akadémiai Kiadó.