A RADIOMETRIC AND PETROGRAPHIC APPROACH TO RISK ASSESSMENT AT ALTE MADONIE MOUNTS REGION (SICILY, ITALY)

The main goal of this work was to assess the radiological hazard at Alte Madonie Mounts region (north-central Sicily, Italy) in response to rumours of an increase in the incidence of cancer in this area. A correlation between the natural radionuclide contents and the petrographic features of the soil and rock samples was also evaluated. A total of 41 samples of selected soils and rocks were collected, powdered, dried and sealed in ‘Marinelli’ beakers for 20 d prior to measurement to ensure that a radioactive equilibrium between 226Ra and 214Bi had been reached. A gamma-ray spectrometer was used to quantify the radioactivity concentrations. To determine 238U and 232Th activities, the 609.3-keV line from 214Bi in secular equilibrium with 226Ra and the 911-keV line from 228Ac, with which 232Th can be assumed to be in equilibrium, were used, respectively. The gamma transition of 1461 keV was used to determine 40K activity. The average values of the concentrations of 214Bi, 228Ac and 40K were 30, 17 and 227 Bq kg–1, respectively, whereas the greatest values were 134, 59 and 748 Bq kg−1, respectively. A linear relationship was found between the activity values of 214Bi, 228Ac and 40K. An exception was found for a group of samples in which the 214Bi activities were much higher than expected. The chemical compositions and mineralogical features of the samples permitted the justification of these anomalies. The results of the primordial radionuclide contents are reassuring from a radiation protection point of view because the activities of the uranium and thorium series products and of the 40K do not present a significant radiological hazard.