137Cs and 226Ra determination in soil and land snails from a radioactive waste site

Environmental radioactivity studies related to nuclear facilities can provide information concerning the transfer of radionuclides to the surrounding soils, water and the local biota. A study of 226Ra, 137Cs and 40K content in soils and in land snails, Helix aspersa Müller, has been performed at the confined Storage Centre for Radioactive Waste (Maquixco, Mexico). At this site, solid and liquid radioactive waste has been stored for two decades; tailing piles of radiometric ore also stood for some time before being buried in specific containers. The nuclear technique used was gamma spectrometry. Atomic absorption spectrophotometry was used for soil and land snails chemical analysis. The preliminary results obtained in soil samples show 226Ra and 137Cs values ranging from 88 to 19 979 and from 89 to 4961 Bq/kg (dry wt.), respectively, depending on the sampling region. For the snails, 226Ra levels in shell samples up to a factor of 9 greater were obtained for the site samples as compared with reference samples collected 100 km away. The results are discussed as a function of the uranium ore tailings localization at the site; a preliminary estimation of concentration factors (soil/snail) is also intended.