Radionuclide Content and Risk Assessment of some Environmental Samples from Gold Mines at Mokuro-Ile-Ife, Osun State, Nigeria

Abstract

Mining and processing of natural resources has being in existence from the beginning of early years with little or no consideration to the possible radiation and contamination being posed into the environment. Using NaI (TI) gamma ray spectrometer, the activity concentration of naturally occurring  radionuclides were determined in soil, rock and water samples from Mokuro gold mines in Osun State, Nigeria. The average activity concentrations of  40K, 238U and 232Th in soil samples were 362.39 ± 83.88, 21.42 ± 6.68 and 17.99 ± 6.68 Bq/kg while in rock samples were 412.62 ± 91.18, 24.61 ± 8.58 and 19.40 ± 6.76 Bq/kg respectively.  For water samples, the mean activity concentrations were in the range of 8.65 ± 4.16 Bq/L, 7.71 ± 3.42 Bq/L, and 102.44 ± 30.50 Bq/L respectively. The annual effective dose contributed by 238U, 232Th and 40K varied from 0.84mSv/y to 0.93mSv/y with an average value 0.88 mSv/y while 232Th varied from 0.018 mSv/y to 0.020 mSv/y with average value 0.019 mSv/y and 40K varied from 0.22 mSv/y to 0.25 mSv/y with an average value 0.233 mSv/y. The 238U contribution to the Annual Effective Dose was very high compared with 232Th and 40K.. The calculated mean of absorbed dose (ADR), Annual Effective Dose (AED), Radium equivalent dose rate (Raeq), Internal and External Hazard Indices in the study area were less than the world averages and the limit recommended by ICRP for all water samples. The data obtained provided the baseline concentration and also indicated that continuous exploration could lead to contamination and eventually be hazardous. .