A SEQUENTIAL EXTRACTION SCHEME TO ASCERTAIN THE ROLE OF ORGANIC-MATTER IN RADIONUCLIDE RETENTION IN MEDITERRANEAN SOILS

A sequential extraction scheme which indicates the role of organic matter in radionuclide retention was applied to two types of Mediterranean soil (sandy-loam and sandy), with low percentages of organic matter and with different contents of clay mineral, which had been previously contaminated with a radioactive aerosol, containing Sr-85, Cs-134, and Ag-110m. Different distributions were obtained for the three radionuclides, depending on the type of soil. Sr-85 was the most available radionuclide for both types of soil, showing significant binding to organic matter in sandy-loam soil. Cs-134 was the most retained radionuclide: for low-organic-matter soils, its availability seemed to depend on clay mineral content. Ag-110m associated with available organic sites showed a positive correlation with organic matter content.