Assessment of radiation hazards associated with tailing and sediment from an abandoned gold mine in Ilesa and an active tantalite mine in Ijero, southwest Nigeria

The implication of indiscriminate or unregulated mining activities has been pointed out as a major risk to human health and the environment. In order to assess the potential radiological hazards pose to the environment due to mining activities in southwest Nigeria, the activity concentrations of 40K, 226Ra and 232Th was determined in tailing and sediment from two mines within the study area. The samples were analysed by gamma spectrometry with low background NaI(Tl) detector. The activity concentrations of 40K, 226Ra and 232Th in all the measured samples ranged from 249.66-1459.25 BqKg-1, 7.62-50.31 Bqkg-1 and 12.68-234.18 Bqkg-1, respectively in soil while in sediment samples, the values ranged from 241.86-1590.40 Bqkg-1, 9.86-74.8 Bqkg-1 and 15.47-145.46 Bqkg-1 for 40K, 226Ra and 232Th, respectively. In order to evaluate the radiological hazards due to the concentrations of natural radionuclides in the samples, the radium equivalent activity, external hazard index, absorbed gamma dose rates and the annual effective dose rates were determined. All these hazard indexes have mean values which are higher than the world average values but are all within their acceptable limits. Document available in abstract form only. (authors)