Determination of radiological hazard levels in soil, mine tailings and rock samples from selected gold mines in Busia district, Uganda

Abstract

This study was designed to determine radiological hazard levels in soil, mine tailings and rock samples from Agata, Okame, Busia 90 and Greenstone Resource Limited Gold mines in Busia District. The specific activity of the radionuclides were determined using Nal (Ti) scintillation detector and the values were then used to determine the radiological hazard parameters due to radionuclides in the samples from the mines under study. The specific activity of 238U in soil, mine tailings and the rock samples from the four gold mines ranged from 18.7 Bqkg-1 to 27.9 Bqkg-1 , 7.4 Bqkg-1 to 13.2 Bqkg-1 and 1.7 Bqkg-1 to 27.8 Bqkg-1 respectively. The specific activity of 232Th in soil, mine tailings and rock samples from the mines ranged from 60.8 Bqkg-1 to 98.8 Bqkg-1 , 25.1 Bqkg-1 to 32.7 Bqkg-1 and 2.3 Bqkg-1 to 66.6 Bqkg-1 respectively while that of4°K in soil, mine tailings and rock samples ranged from 53.6 Bqkg-1 to 211.8 Bqkg-1 , 5.7 Bqkg-1 to 217.3 Bqkg-1 and 2.1 Bqkg-1 to 120.1 Bqkg-1 respectively. The Specific activity values of 232Th in soil sample from each of the four gold mines were above the worldwide average value of 30 Bqkg-1 . It is only Greenstone mine tailings and Okame rocks that had higher activity for 232Th than the world wide average value. The Absorbed Dose rates in soil, rock and mine tailings samples ranged from 41.7 nGyh-1 to 76.3 nGyh-1 , 13.3 nGyh-1 to 32.7 nGyh-1 and 2.3 nGyh-1 to 58.0 nGyh-1 respectively. Only Okame had a higher value for soil than the world wide average value of 60 nGyh-1 • The Annual Effective Dose rates in soil, mine tailings and rock samples ranged from 0.051 mSvy-1 to 0.093 mSvy-1 , 0.024 mSvf1 to 0.050 mSvf1 and 0.011 mSvy-1 to 0.047 mSvf1 respectively which were lower than the ICRP recommended value of 20 mSvf1 • The internal hazard indices in soil, mine tailings and rock samples ranged from 0.30 to 0.56, 0.15 to 0.27 and 0.02 to 0.43 respectively. External hazard indices of the radionuclides in the soil, mine tailings and rock samples ranged from 0.27 to 0.47, 0.10 to 0.23 and 0.01 to 0.36 respectively. They were found to be below unity as per ICRP, 2007 maximum permissible limit. The Excess Lifetime Cancer Risk (ELCR) ranged from 6.90x10-5 to 1.93x104 was lower than the ICRP maximum permissible excess lifetime cancer risk limit of 5.60x10-2 . Despite the low radiological health risk, miners need protective gears particularly at Okame and Greenstone mines and further research need to be done to validate these findings.