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 226Ra, 232Th and 40K was performed using the gamma-ray spectrometer equipped with a high purity germanium detector. The values of the activity concentration of 226Ra ranged from 24.69±4.26 to 82.20±15.62 Bqkg-1, with a mean of 47.06±14.01 Bqkg-1; 232Th ranged from 22.52±3.44 to 159.47±16.81 Bqkg-1, with a mean of 75.97±9.11; while 40K 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.   Key Words: Anka, artisanal mining, radioactivity, radiological, radionuclide, soil.