Evaluation of Radioactivity in Montenegro Soil Using a Statistical Approach

Abstract

Surface soil from 47 locations in Montenegro had been previously analyzed for radioactivity due to natural 226 Ra, 232 Th, 40 K and man-made 137 Cs, and showed mean activity concentrations around 41.1, 45.8, 500 and 95.2 Bq/kg, respectively. Discriminant Analysis used in the present study for the classification, with activity concentrations of radionuclides as independent variables and the Montenegro region (South, Center, North) as a grouping variable, showed 76.6% of original grouped cases as correctly classified. The radium equivalent activity, external and internal hazard index showed a mean of 142 Bq/kg, 0.39 and 0.5, respectively. An average external terrestrial gamma absorbed dose rate was found to be 67.5 nGy/h -for natural radionuclides only, and 79.3 nGy/h for natural radionuclides and 137 Cs. The corresponding annual effective dose showed a mean of 0.08 mSv and around 0.1 mSv, respectively. These hazard indices, together with radionuclide activities, are used in the factor analysis performed with Principal Component Analysis as the extraction method and Varimax with Kaiser Normalization as the rotation method. Two components were extracted. The first one loaded basically on 232 Th and 226 Ra activity explained 80.6% of the total variance, while the second component explaining 12.2% of the total variance is found to be strongly correlated with 137 Cs and 40 K activity.