In situ biological monitoring of radioactivity and metal pollution in terrestrial snails Helix aspersa from a semiarid ecosystem

¹ ININ, Ap. Post. 18-1027, 11801 Mexico D.F., Mexico
² IGF-UNAM, Ciudad Universitaria, 04510 Mexico D.F., Mexico

Abstract

Soil samples and wild terrestrial snails from a storage centre for radioactive waste site, located in a semi-arid region of Central Mexico, have been analysed as indicators of trace metals pollution and radioactivity. In order to observe, under natural field conditions, the effect of uranium ore tailings and caesium in the soil and snails, some trace element concentrations and specific activities of ²²⁶Ra, ¹³⁷Cs and ⁴⁰K were measured in the soil, soft tissue and shell. The methodologies include the use of an atomic absorption spectrophotometer, an ICP-MS, an X ray fluorescence spectrometer and a gamma ray spectrometer. The concentration of some toxic elements (Ba, Cd, Cr, Ni, Pb and V) in the soft tissue is higher than the toxic level for these elements. Compared with other wild food, snails have relatively high transfer factors for some elements. The importance of this food to the diet, would tend to confirm that its consumption represents an important pathway for the intake of natural and anthropogenic toxic elements and for the delivery of the internal doses to man. The annual effective dose for ²²⁶Ra due to ingestion of the snails represents 39% of the total annual dose from food intake (0.3 mSv).