Assessment of radiological risk from the soils of artisanal mining areas of Anka, North West Nigeria

Abstract

Assessment of radiological risk was carried out on twenty soil samples collected from agricultural, mining and mine processing areas in Anka, Zamfara State, North Western Nigeria. The measurement of activity concentration of 226 Ra, 232 Th and 40 K was performed using the gamma-ray spectrometer equipped with a high purity germanium detector. The values of the activity concentration of 226 Ra ranged from 24.69±4.26 to 82.20±15.62 Bqkg -1 , with a mean of 47.06±14.01 Bqkg -1 ; 232 Th ranged from 22.52±3.44 to 159.47±16.81 Bqkg -1 , with a mean of 75.97±9.11; while 40 K ranged from 27.20±8.03 to 542.64±156.93 Bqkg -1 , with a mean of 216.02±62.37 Bqkg -1 . The concentration of the Radium equivalent in the study area ranged from 60.41 to 307.30 Bqkg -1 , with mean value of 172.33 Bqkg -1 . The absorbed dose rate in air was calculated and the values ranged between 26.80 and 135.02 nGyh -1 , with a mean of 76.64 nGyh -1 . The external hazard index was computed and the values ranged from 0.163 to 0.830, with a mean of 0.465. This value is within the safe limit of 1. The annual effective dose rate was calculated from the activity concentration with the minimum value of 32.87 µSvy -1 , while the maximum was 165.58 µSvy -1 , with a mean of 93.99 µSvy -1, which is higher than the world average of 80 µSvy -1 but less than the recommended annual effective dose safe limit of 1 mSvy -1 . Therefore, the soil does not constitute radiological threat to the local population in the environment.

Analysis of Radiological Hazard Indices from Mining Sites in Adamawa State, Nigeria

“…The average activity concentration of Ra-226, Th-232 and K-40 obtained in this study is higher than that obtained in Nigeria by Mbet et al [12], Ibikunle et al [13] and Oluyide et al [19] in Nigeria and Harb et al [20] in Egypt. The average activity concentration of Ra-226, Th-232 and K-40 from this study are higher than the median values throughout the world according to UNSCEAR [10].…”

“…External Hazard Index was below the recommended value of 0.45, Annual effective dose rate was below the recommended public dose limit of 1mSv/y as recommended by ICRP, while Excessive Life Cancer Risk was above the recommended value of 0.29. Comparison of the results of radiological hazard indices with published data from similar investigations in Nigeria shows higher Gamma Absorbed Dose Rates reported by Mbet et al [12] in Anka, Solomon et al [14] in Jos and Shittu et al [17] in FCT Abuja, while lower dose was recorded by Ode et al [16] in Benue and Usikalu et al [18] in Ogun. For the Radium Equivalent Activity, higher values were reported by Mbet et al [12] in Anka, Solomon et al [14] in Jos and Shittu et al [17] in FCT Abuja, while lower values were reported by Ibikunle et al [13] in the South West and Ibrahim et al [3] in Nasarawa.…”

“…Comparison of the results of radiological hazard indices with published data from similar investigations in Nigeria shows higher Gamma Absorbed Dose Rates reported by Mbet et al [12] in Anka, Solomon et al [14] in Jos and Shittu et al [17] in FCT Abuja, while lower dose was recorded by Ode et al [16] in Benue and Usikalu et al [18] in Ogun. For the Radium Equivalent Activity, higher values were reported by Mbet et al [12] in Anka, Solomon et al [14] in Jos and Shittu et al [17] in FCT Abuja, while lower values were reported by Ibikunle et al [13] in the South West and Ibrahim et al [3] in Nasarawa. In terms of External Hazard Index, higher values were reported by Solomon et al [14] in Jos, while lower values were reported by Mbet et al [12] in Anka, Ibikunle et al [13] in the South West, Ode et al [16] in Benue, Shittu et al [17] in FCT Abuja, Usikalu et al [18] in Ogun, and Ibrahim et al [3] in Nasarawa.…”

“…Comparison of the results of activity concentrations of Ra-226, Th-232 and K-40 in soil samples with published data from similar investigations in Nigeria, Gabon, Egypt, China, Pain, Japan and India and the median values throughout the world according to UNSCEAR [10] shows higher activity concentration for Ra-226 determined by Mouandza et al [15], while that of Th-232 Mbet et al [12] and K-40 by Okeme et al [2] in Nigeria respectively, However, lower activity concentration was determined by Ibikunle et al [13] and Oluyide et al [19] in Nigeria and Harb et al [20] in Egypt. The average activity concentration of Ra-226, Th-232 and K-40 obtained in this study is higher than that obtained in Nigeria by Mbet et al [12] Ibikunle et al [13] and Oluyide et al [19] in Nigeria and Harb et al [20] in Egypt. The average activity concentration of Ra-226, Th-232 and K-40 from this study are higher than the median values throughout the world according to UNSCEAR [10].…”

“…Comparison of the result of activity concentrations of Ra-226, Th-232 and K-40 in soil samples obtained at different sampling points from four selected mining locations in Adamawa State with published data from similar investigations in Nigeria, Gabon, Egypt, China, Pain, Japan and India and the median values throughout the world according to UNSCEAR [10] were presented. Higher activity concentration for Ra-226 was determined by Mouandza et al [15] in Gabon, while that of Th-232 was determined by Mbet et al [12] and that of K-40 was determined by Okeme et al [2] in Nigeria respectively, while lower activity concentration was determined by Ibikunle et al [13] and Oluyide et al [19] in Nigeria and Harb et al [20] in Aswan, Egypt.…”