Environmental Radiation Dose Rate In The Gold Mining Region Of Lolgorian In Narok County

Abstract

Exposure to radiation leads to harmful health effects on human beings, either deterministic or stochastic depending on the threshold of the radiation dose. Knowledge on the radiation profile of a particular working environment should be a requirement to both the radiation regulatory authorities and the occupational workers. Currently there exists little to none radiological information on the gold mining region of Lolgorian. This study serves to bridge this gap in knowledge and data from the mining region. This study was done in the gold mining region of Lolgorian in Narok County, specifically to determine radioactivity concentrations of thorium, potassium and uranium radionuclides, and to evaluate the associated radiation hazard indices. The study was done by analyzing thirty six (36) soil samples from Lolgorian for radioactivity measurements using hyper pure germanium detector. The greatest contributor to radiation exposure in the vicinity of Lolgorian gold mines was 40K, with a mean activity concentration of 427 ± 116 Bq kg-1 (74%), as compared to 232Th and 238U at 116 ± 69 Bq kg-1 (20%) and 33 ± 22 Bq kg-1(5%) respectively. The 238U activity concentration was within the UNSCEAR global mean of 35 Bq kg-1, while 232Th and 40K radionuclides were slightly above the global mean of 30 Bq kg-1 and 400 Bq kg-1 respectively. Radium equivalent values ranged between 38 – 529 Bq kg-1, with a mean of 232 ± 38 Bq kg-1; which is above the world mean reported at 160 Bq kg-1, but within the UNSCEAR permissible limit of 370 Bq kg-1. Gamma radiation index Iγr was determined to have a mean of 1.66 ± 0.28, hence exceeding the required index value of unity (≤1). Internal and external hazard index were determined to be 0.72 ± 0.14 and 0.62 ± 0.11 respectively. The absorbed dose rates at 1 m distance above the ground level was determined at between 19 nGy h-1 and 156 nGy h-1. The annual effective dose using an outdoor occupancy factor of 0.4 had a mean value of 0.25 ± 0.04 mSv y-1, which is below the mean global annual effective dose at approximately 0.5 mSv y-1. Fe was the major constituent in the soil samples, followed by Ti and Mn, with a mean concentration of 9.22 ± 7.70 %, 4370 ± 2500 mg kg-1, and 1869 ± 1509 mg kg-1 respectively. Other mean concentrations below 100 mg kg-1, were recorded for Zn, Zr, Rb and Pb. Zn concentrations ranged between (20 – 792) mg kg-1, with a mean of 102 mg kg- v 1. The study concluded that the radioactivity levels in the gold mining region of Lolgorian in Narok County currently do not pose significant risk to the public. However, there is need to analyze radioactivity levels in water sources to get a complete understanding of the extent of radioactivity distribution. Continuous periodic monitoring of the region’s radionuclide concentration is recommended.