Forms and rates of release of 137Cs in two peat soils

Cation exchange resin saturated with H+ and Ca2+ was used to extract Cs-137 from peat soil at two sites in Britain affected by Cs-137 deposition following the Chernobyl accident. The technique identified three classes of Cs-137, similar to those observed for K+ in soils: 'Fast', 'Intermediate' and 'Slow'. These classes are probably related to the selectivity for Cs-137 Of the cation exchange sites on the organic matter and the clay minerals, and to the structure of the soil. With one exception, most Cs-137 was in the 'Slow' form and was only very slowly released to the resins, if at all. However, there was enough Cs-137 in the 'Fast' and 'Intermediate' forms to contaminate pasture and thus grazing animals for some years. Based on the resin technique, it is estimated that contamination will persist for several decades in uplands contaminated at these activity concentrations.