Natural radioactivity levels and the radiological health implications of tailing enriched soil and sediment samples around two mining sites in Southwest Nigeria

Abstract

The activity concentrations of natural radionuclides in tailing enriched soil and sediment samples collected from two mining sites in southwest Nigeria are reported. The samples were analyzed by gamma spectrometry with low background NaI (Tl) detector. The activity concentrations of 40 K, 226 Ra and 232 Th in all the measured samples varied from 249.66 to 1459.25 Bq/kg, 7.62 to 50.31 Bq/kg and 12.68 to 234.18 Bq/kg, respectively in soil samples. For sediment samples, the values varied from 241.86 to 1590.40 Bq/kg, 9.86 to 74.8 Bq/kg and 15.47 to 145.46 Bq/kg for 40 K, 226 Ra and 232 Th, respectively. The results show that the mean activity concentrations of the radionuclides in soil and sediment of the study area are higher than their world-wide average crustal values. The mean concentration of 232 Th is >6 times higher than that of 226 Ra in soil samples from Ijero mining site. This shows that 232 Th is slightly enhanced in the soil from this location than 226 Ra. In order to evaluate the radiological hazards of the natural radioactivity, the radium equivalent activity, external hazard index, absorbed gamma dose rates and the annual effective dose rates were determined. All these hazard indices have mean values, which are within their acceptable limits but higher than their world average values.