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

Abstract

Abstract The activity concentrations of natural radionuclides 238U, 232Th and 40K 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 226Ra, 232Th and 40K 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 226Ra, 45Bq/kg for 232Th and 420Bq/kg for 40K. Radiological hazard assessments due to these natural radionuclides were carried out. The radium equivalent activity (Raeq), external hazard index (Hex), internal hazard index (Hin) 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 Raeq, Hex, Hin 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 Raeq, ≤ 1 for Hex, ≤ 1 for Hin and ≤ 1 for Iγ respectively. Absorbed Dose Rate in Air (DR), 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 DR, 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 DR, 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.