Determination of natural radioactivity levels and radiological hazards in environmental samples from artisanal mining sites of Anka, North-West Nigeria
MbetAmos Akpanowo, Ibrahim Umaru, Shekwonyadu Iyakwari, E. O. Joshua, Samson Dauda Yusuf, Godwin Bassey Ekong
Abstract
Artisanal mining of precious metals has become a lucrative venture in Anka, Zamfara State, North-West Nigeria. The use of crude methods of mining and mineral processing and the apparent ignorance of the hazards involved have been linked to some health and environmental consequences. Hence, this study focuses on the assessment of radioactivity levels in rock, soil and sediment samples as well as the radiological hazards of the artisanal mining in Anka. The gamma-ray spectrometry method was employed in the sample analysis. The results show that the estimated mean activity concentrations of 226Ra, 238U, 232Th and 40K in soil were 37.94 ± 6.01 Bqkg−1, 41.60 ± 11.06 Bqkg−1,151.15 ± 21.09 Bqkg−1 and 380.34 ± 116.41 Bqkg−1, respectively. The activity concentrations in rocks and sediments were also analyzed. The radioactivity levels were highest in rock samples. ; For rock samples, mean radium equivalent was 499.18 Bqkg−1, gamma dose rate was 221 ± 35 nGyh−1, internal and external hazard indices were 1.35 and 1.53, respectively and the radioactivity level index was 3.24. The outdoor and indoor annual effective dose equivalents were 271.03 µSvy−1 and 985.39 µSvy−1, respectively. The mean indoor and outdoor excess lifetime cancer risk for soil were 0.55 × 10−3 and 2.18 × 10−3. The evaluation of radiological health risks shows that the values obtained in this study were generally higher than admissible recommended limits and the world averages. The results obtained in this study show that the risk of exposure to ionizing radiation is linked to the artisanal mining and mineral processing in Anka.