Determination of Natural Radioactivity Levels and Radiation Hazards from the Soil of Tin Mining in Kyerwa District, Tanzania

The activity concentrations of natural radionuclides 238 U, 232 Th and 40 K in soil samples from the Tin mining in Kyerwa District were measured by gamma spectrometry using Sodium Iodide detector. The results showed that, the mean activity concentrations of 226 Ra, 232 Th and 40 K were 90.68, 65.45 and 630.95Bq/kg, respectively. All the activity concentrations in the studied samples were higher than the world average values of 32Bq/kg for 226 Ra, 45Bq/kg for 232 Th and 420Bq/kg for 40 K. Radiological hazard assessments due to these natural radionuclides were carried out. The radium equivalent activity ( Ra eq ), external hazard index ( H ex ), internal hazard index (H in ) and radioactivity level Index (Iγ) were calculated to assess the radiological hazards due to presence of natural radionuclides in the soil samples. The results showed that the mean values of Ra eq , H ex , H in and Iγ were 230.6, 0.628, 0.861 and 0.831Bq/kg, respectively. These values were lower than the world criteria values 370 for Ra eq , ≤ 1 for H ex , ≤ 1 for H in and ≤ 1 for Iγ respectively. Absorbed Dose Rate in Air (D R ), Annual Effective Dose Equivalent (AEDE) and Annual gonadal equivalent dose (AGED) were also estimated for the mining areas in Kyerwa. The results showed that the mean values for D R , AEDE and AGED were 106.8nGy/h, 1.07mSv/y, and 744.4µSvy-1 respectively. The mean values were higher than those of the worldwide average which are 57 nGyh − 1 for D R , 0.07mSv/y for AEDE and 2984µSvy-1 for AGED. Therefore, mining activities in Kyerwa District can poses radiological hazard to the mining community. In this study therefore, we recommend performing periodical inspection at the mining areas, monitoring of the mining workers and the level of activity concentrations of different radionuclides in the mining area.