Abstract:
Peoples continuously exposed to gamma radiation emitted from primordial radionuclides uranium-238, thorium-232 and potassium-40 in soil. Natural environmental radiation and the associated external exposure due to gamma radiation depend primarily on the geological and geographical conditions and human activities. In this study, the activity concentrations of 238U, 232Th and 40K radionuclides were determined in five soil samples collected from some parts of Gore town at the local name Airport, Central market, farm land, Gummaro tea plantation and Mettu university main campus south west Ethiopia using High purity Germanium (HPGe) detector. The average activity concentration of 238U, 232Th and 40K in the soil samples were 83 ± 4.2, 115 ± 5.9 and 204 ± 10.3 Bq/kg, respectively. These values were higher than the warld average recommended values for 238U, 232Th and 40K respectively which are 35, 30 and 400Bq/kg for 238U, 232Th and 40K respectively [UNSCEAR, 2000]. The average value of radium equivalent for the soil samples in area under investigated was 263.16 ± 17.23Bq/kg which is lower than the recommended maximum value 370 Bq/kg [Gilmore, G.R., 2008]. The calculated values of Dr were found to have an average of 116.32 ± 5.9 nGy/y. According to (sulaiti, et al., 2008) the published maximal admissible dose rate is 55nGy/h. The average dose rate determined for the samples in this work is higher than the worldwide value. The averag annual effective dose was found to be 142.65±7.25μSv/y which is lower than the world average value which is 460μSv/y. The external hazard index average value 0.71 ± 0.03 for the study soil samples was less than the world recommended value which is unity. The calculated internal hazard index average value is 0.93 ± 0.04, which is less than world recommended value unity [Dabayneh K et al,.2008]. The average gamma index of the study soil was 1.53 ± 0.087 which is higher than recommended world wide average value≤1. Hence, it can be concluded that the radionuclide concentration of the study area is negligible and poses no radiological health hazard to the community.
