Comparative analysis of NORM concentration in mineral soils and tailings from a tin-mine in Nigeria.

Abstract

Mining of tin and other related activities have been active and thus leading to economic growth in the Jos area of Nigeria for more than a century. However, mining of minerals has been confirmed to enhance the concentrations of heavy metals and natural radioisotopes in the soil, air and water bodies in the environment. In an attempt to evaluate the radiological burdens resulting from tin mining activities at Rayfield-Du area of Jos, specific activities of naturally occurring radioactive nuclei (238U, 232Th and 40K) concentrations were evaluated in soil samples collected from the mine site. The soil samples were classified as normal soil (S), tailings (T) and mineral soils (M) and their corresponding mean activities for 238U, 232Th and 40K were analysed using an HpGe detector-based gamma spectrometric system. The mean activity concentration for 238U, 232Th and 40K were 323.44, 877.63 and 864.99 Bq/kg, 138.84, 469.31 and 578.65 Bq/kg and 168.83, 436.08 and 346.1 Bq/ kg, respectively for M, T and S samples. The calculated radiation dose parameters for the soil samples were all higher than the recommended safety limit. For all the collected soil samples, the external hazard risk Hext were 2.21, 2.81 and 4.44 for S, T and M, respectively while the mean calculated radium equivalent was 819, 1057 and 1645 Bq/kg for S, T, and M, respectively. The excess lifetime cancer risk estimated for the mine was more than the world average value. The radio-ecological dose rate estimate for non-human biota in the mine revealed that all non-human species except lichen and bryophyte had absorbed dose rate less than the 10 µGy/h screening dose.