Evaluation of Naturally Occurring Radionuclide Materials in Soil Samples Collected From Some Mining Sites in Zamfara State, Nigeria

Aims: To identify and quantify prominent gamma emitting-NORMs associated with mining activities in Zamfara State, Nigeria.
Study Design: Soil samples were collected from 10 different mine sites in Zamfara State, northwest-Nigeria for gamma spectroscopy analysis.
Place and Duration of Study: Department of Physics, Nigerian Defence Academy Kaduna, Nigeria, between June 2012 and October 2012.
Methodology: A laboratory based γ-ray spectrometry NaI(Tl) at the Centre for Energy Research and Training (CERT), Ahmadu Bello University Zaria, Nigeria was employed to carry out the analysis of the soil samples.
Results: The values of activity concentration found for 40K, 238U and 232Th range from 227.10±7.54 – 590.44±10.57, 4.68±3.52 – 18.98±0.84 and 40.58±1.85 – 94.92±2.75 Bq.kg-1 respectively, while absorbed dose rate in the soil samples for 40K, 238U and 232Th range from 9.47±0.31 – 24.62±0.44, 2.16±1.62 – 8.77±0.39 and 24.51±1.12 – 57.33±1.66 nGy.h-1 respectively. The total average absorbed dose rate of the soil samples collected is 59.70 nGy.h-1 and the estimated annual effective dose for the study areas range from 52 – 106 μSv.y-1, with an average annual effective dose of 73 μSv.y-1.
Conclusion: The radiation exposure level for members of the public in the study areas is within the safety limit.