Assessment of solid mineral to soil radioactivity contamination index in selected mining sites and their radiological risk indices to the public

This study examined the radioactivity levels of soil samples within selected solid mining sites in Nigeria using high-purity germanium (HpGe) detector. Sixty soil samples in all were collected from the 10 solid mineral mining sites investigated and six samples were collected as control samples from non-mining environment for analyses. The results of the activity concentration values obtained for K-40, Ra-226 and Th-232 are 100.22 Bq kg(-1), 33.15 Bq kg(-1) and 77.31 Bq kg(-1), respectively. The Ra-226 and K-40 activities were found to be within the United Nation Scientific Committee on the Effects of Atomic Radiation acceptable permissible limit, but the Th-232 mean value was above the permissible limit of 30 Bq kg(-1) for the public. In comparison, K-40, Ra-226 and Th-232 soil samples mean activity concentrations were higher than the control soil samples values by 48.6%, 43.7% and 62.3%, respectively. The results of estimated radiation hazard indices indicate average values of 150.72 Bq kg(-1), 68.40 nGyh(-1), 83.65 mu Svy(-1) and 454.70 mu Svy(-1) for the Radium Equivalent (Ra(eq)Raeq), Absorbed Dose Rate (D), Dose Equivalent (AEDE) and Annual Gonadal Equivalent Dose (AGED), respectively. The mean values for External Hazard Indices (Hex, Hin), Representative Gamma index (I gamma) and Excess Life Cancer Risk (ELCR) were 0.41, 0.50, 1.06 and 0.29 x 10(-3), respectively. The statistical analysis shows positive skewness.