Mobility of Cs-137 related to speciation studies in contaminated soils of the Chernobyl area

Chernobyl derived Cs-137 present in upper soil layers can still remain avai lable to cation exchange and hence to downward migration. More than its phy sico-chemical deposit forms (fuel particles and/or condensed aerosols), rad iocesium mobility is influenced by soil properties. Although all the soils studied contain illitic clay minerals, different Cs-137 fixation levels wer e observed due to: (1) the reactivity state of sorption sites with a low ra diocesium content in soil, and (2) the presence, or absence, of organic mat ter complexes inhibiting cation sorption on clays.