Natural radioactivity in the soil samples of Botswana

Studies on concentrations of primordial radionuclides in soil samples of Botswana were carried out. Measurements were made by gamma spectrometry employing a 41% relative efficiency HPGe detector. The activity of 226Ra was found to vary in the range 6.1–97.4 Bq kg−1 with a mean value of 34.8 Bq kg−1, 232Th in 7.4–110.0 Bq kg−1 with a mean value of 41.8 Bq kg−1 and that of 40K between 33.5 and 1085.7 Bq kg−1 with a mean value of 432.7 Bq kg−1 in surface soils. Existence of strong correlations in the distributions of these radionuclides indicates that an individual result for any one of the radionuclide is a good predictor of the concentration of the other. The mean value of effective dose, due to the 238U series, 232Th series and 40K in soil, was 0.07 mSV. The results of the present study are compared with the literature values reported for other normal background regions of the world and discussed.