Gamma ray spectrometric analysis and assessment of radiation hazards in soils of Mbeere North region, Kenya

Abstract This study used gamma ray spectrometry to determine the radiological safety of construction soil sampled randomly from Mbeere North region, Kenya. The mean activity concentration of 232Th, 238U, and 40K was 149.7 ± 2.8 Bqkg−1, 88.3 ± 2.4 Bqkg−1, and 490 ± 35 Bqkg−1, respectively. These averages exceed the world average for all the radionuclides. The radionuclides were non-uniformly distributed, with higher concentrations along the slopes and on the feet of the hills. The mean absorbed dose rate, indoor and outdoor annual effective dose, radium equivalent, external hazard index, and internal hazard index were 157.9 ± 4.4 nGh−1, 0.58 ± 0.02 mSvy−1, 0.39 ± 0.01 mSvy−1, 340.7 ± 9.2 Bqkg−1, 0.92 ± 0.02 and 1.14 ± 0.03, respectively. Among the radiation safety indicators, only the average internal hazard index exceeded slightly the acceptable safe limit. Therefore, soils of Mbeere North region are radiologically safe for use in brick making and construction of human habitats.