Determination of the Activity Concentrations of Radon-222 and Radon-220 in Water and Soil Samples from Newmont-Akyem Gold Mine Using Gamma Spectrometry

Abstract

In this study a total of 28 water and soil samples were analysed by High Purity Germanium (HPGe) detector for 222Rn (Radon), 220Rn (Thoron) and other natural radionuclides (226Ra, 232Th plus 40K) activity concentrations. The data generated was then used to assess radiological hazards posed to the public. The radon (Rn-222) concentration in the surface water varied from 0.015 to 1.701 Bq/L with a mean value of 0.913 ± 0.605 Bq/L against the global average of 11 Bq/L and thoron (Rn-220) was not detected in the surface water. For the soil samples, the concentration of radon ranged from 4.194 to 21.114 kBqm3 with mean value of 10.829 ± 4.130 kBq/m3 while thoron ranged from 0.544 to 13.222 kBq/m3 with the mean value of 5.062 ± 3.051 kBq/m3. In order to assess hazards due to radon concentration in the water to the people, the annual effective doses (AED) were computed. For ingestion of radon in water the AED varied from 0.019 to 4.346 μSv/y with a mean value of 2.333 ± 1.546 μSv/y while for inhalation of radon from water varied from 0.019 to 2.146 μSv/y with mean value of 1.152 ± 0.763 μSv/y respectively. The total AED due to ingestion and inhalation of radon in water ranged from 0.057 to 6.492 μSv/y with a mean value of 3.486 ± 2.309 μSv/y. Most people in the study area use soil as building material, thus the assessment of Radium equivalent activity ( ) and Internal hazard index ( ), which are related to radon gas were carried out. The results varied from 19.708 to 69.880 Bq/Kg with mean value of 37.527 ± 15.508 Bq/Kg for which is lower than the global limit of 370 Bq/Kg. The ranged from 0.065 to 0.248 Bq/Kg with a mean value of 0.132 ± 0.053 Bq/Kg, also lower than the agreed global value of one (1). The study also assessed AED due to external and internal gamma and the values ranged from 0.060 to 0.175 mSv/y with a mean value of 0.11 ± 0.025 mSv/y against the global value of 1 mSv/y. Since Annual Effective Dose due to inhalation of indoor radon from soil gas was not conducted it is difficult to conclude whether people at Akyem are safe from radon. However the results for water and soil gas radon have shown that the people may safely use the water for drinking and soil for building dwellings with very minimal radiological hazards.