Radiological Impact Assessment of Mining on Soil, Water and Plant Samples from Okobo Coal Field, Nigeria

Abstract

Anthropogenic, including mining activities leaves the environment contaminated with potentially toxic substances and remote hazards if not properly checked. The quest in this study is the levels of naturally occurring radionuclides in Okobo coal, Nigeria and their possible distribution in coal mine vicinity soils, water and plants (cassava). Samples were characterized for levels of radionuclides and radiological detriments using high resolution gamma spectrometer, Gamma ray liquid scintillation and applicable radiological hazard indices. The range of mean activity concentrations (Bq·kg−1) for the environmental samples are as follows: 226Ra (8.39 ± 1.0 to 77.6 ± 4.0), 232Th (0.470 ± 0.4 and 77.8 ± 2), and 40K (29.1 ± 0.4 and 289 ± 6), with their respective mean values of 32.7 ± 2.1, 54.0 ± 1.5 and 158.8 ± 3.1 (Bq·kg−1). Radiological detriments including radium equivalent activity (Raeq), external hazard index (Hex), internal hazard index (Hin), radioactivity level index or gamma index (Iγ) and the ELCR for coal sample is 96.94 Bq·kg−1, 0.26, 0.30, 0.69, and 1.56 respectively. Reported values were below the safety limits stipulated by UNSCEAR and implied that the environment is relatively safe with low levels of natural radioactivity. Overall, this background study has demonstrated that Okobo coal mine is a less radio-hazard contributor to environmental samples. Exceptions to this generalization are representative gamma index (Iγr) and annual effective dose equivalent values for some cassava and soil samples, which may call for future impact monitoring.