Evaluation of the Activity Concentration of ⁴⁰K, ²²⁶Ra and ²³²Th in Soil and Associated Radiological Parameters of Shanono and Bagwai Artisanal Gold Mining Areas, Kano State, Nigeria

Abstract

Mining in the studied area is carried out without any precautionary measure. The radiological implication of this activity was reported in this work. Soil samples were collected from the gold mines and analyzed for activity concentration of naturally occurring radioactive materials (NORMs) using NaI (Tl). The average specific activity of 238 U, 232 Th and 40 K were 62.73, 90.66 and 411.27 Bq/kg respectively. The radiological parameters D (nGy/h), AED (mSv/y) and Raeq had average values of 100.89, 0.13 and 224.04 respectively. Furthermore, the radiological hazard indices Hex, Hin, Iγ and Iα had average values of 0.61, 0.78, 0.86 and 0.31 respectively, which were lower than the United Nations Scientific Committee on effects of atomic radiation (UNSCEAR) recommended limit of unity. Finally, the total cancer risk due to NORMs in soil was 7.35 × 10 for the whole populations which was within the USEPA acceptable range of 1.00 × 10 to 1.00 × 10. Therefore, the gold mining activity poses no significant radiological hazard to the members of the public.

Review of Distribution of Natural Radiation in Some Parts of Nigeria

“…Table one the comparison of activity concentrations of primordial radionuclides in rocks, soil, and sediments carried out by various researchers obtained from some Northern and Southern part of Nigeria. The mean activity concentration of 40 K is higher in rock samples in the North-Central region of the country in Nassarawa with a value of 8504.88 Bqkg -1 and Ikogosi in South-West with a value of 1203Bqkg -1 than other locations. The mean activity concentration of 228 U is higher in rock samples in the Northern region with a mean value of 7220 Bqkg -1 in Jos, this value is higher than IAEA 1000 Bqkg -1 and a mean value of 557.9 Bqkg -1 in Sokoto; while it is relatively low in other locations.…”

“…The mean activity concentration of 232 Th in the soil is higher in Oyo with a mean value of 195.3 Bqkg -1 than values from all other regions in Nigeria. In sediment samples, the mean activity concentration of 40 K is high in all Sothern regions, while the mean activity concentration of 238 U and 232 Th is entirely at the acceptable recommended level. Comparative distribution maps are given for the concentration of 40 K, 238 U, and 232 Th in figure 1, figure 2, and figure 3.…”

“…Number of samples Table 2 shows the mean specific activity contents (Bq l -1 ) in various water supplies in Ife local government areas. The result shows that the most significant contribution to the overall activity in all the various types of water samples came mainly from 40 K with the lowest value of 48.39 5.45 Bql -1 , the highest being 109.39 2.41 Bq l -1 compared to the activity ranges of 2.90-15.84 Bql -1 and 0.3-3.89 Bql -1 for 226 Ra and 228 Ra, respectively. It is because most of the various water samples in the study were collected from soils that are mostly granite rocks, which contains high levels of 40 K [27].…”

“…The average concentrations of radionuclides different types of water were investigated in Ife local government areas [26]. 40 K, 226 Ra, and 228 Ra were observed in water samples from the dam, streams, boreholes, wells, and tap, as shown in Table 2. Table 2.…”

“…It is because most of the various water samples in the study were collected from soils that are mostly granite rocks, which contains high levels of 40 K [27]. Hence, 40 K contributes to humans the highest radiation dose from ingestion. 40 K is a naturally occurring radionuclide which abounds in the earth's crust and the human body [28,29].…”