Radiometric and Radiogenic Heat Evaluation of Natural Radioactivity in Soil Around Solid Minerals Mining Environment in South-Eastern Nigeria

摘要

Radionuclides activity concentrations in soil around ten solid mineral mining sites have been investigated using sodium iodide [Na(TI)] gamma spectroscopy. Four soil samples and a control sample were collected from each of the selected sites for analyses. The obtained results showed mean concentration values of 33.2 Bq kg_(−1)for_(226)Ra, 100.7 Bq kg_(−1)for_(40)K and 77.7 Bq kg_(−1)for_(232)Th. The estimated radiological risk parameter results have shown average values of 67.5 η Gy h _(−1)for the Absorbed Dose Rate (D~(R)), 82.8 μSv y_(−1)for the Annual Effective Dose Equivalent (AEDE), 151.4 Bq kg_(−1)for the Radium Equivalent (Ra~(eq)) and 457.1 mSv y_(−1)for the Annual Gonadal Equivalent Dose (AGED) which is highly comparable to the allowable WHO value of 300 mSv y_(−1)and the control value of 177.7 mSv y_(−1). The average Excess Life Cancer Risk (ELCR) value obtained was 289.6 × 10_(−6)and the control value 112.9 × 10_(−6). The average External Hazard Index (Hex), Internal Hazard Index (Hin), Representative Gamma index (  I ~( γ )), and Activity Utilization Index (AUI) obtained were 0.4, 0.5, 1.1 and 1.3, respectively. The Radiogenic Heat produced Q ranged from 248.4 pW kg_(−1)in Awkuke (ironstone mine) to 608.5 pW kg_(−1)in Ama-Echi (Silica mine) with an average heat value of 415.8 pW kg_(−1). The obtained result for lithology [clay] identification showed a mixed clay lithology type. The overall results were found to be higher when compared to previously reported values from similar mineral mining areas, which indicates radiological contamination.