The influence of clay mineralogy on the mobility of radiocaesium in uplandsoils of NW Italy

Cs-137 extraction experiments were performed on 14 contaminated soils from NW Italy with different characteristics and mineralogical composition. Solu tions of HCl (pH=0.5) and buffered EDTA/ammonium acetate (Lakanen solution) were used to assess bioavailability. The results show that less than 2% of Cs-137 is available for leaching and/or root uptake. Even within a complex natural system it was possible to identify the amount of swelling clays (v ermiculite+ smectite) as the main control on Cs mobility under acidic condi tions. The ammonium ion appears to be effective in desorbing Ca and its rol e is briefly discussed in terms of crystal chemistry. The relevance of mine ralogy in assessing soil vulnerability is underlined. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.