Radioactivity concentrations and dose assessment for bitumen and soil samples around a bituminous deposit in Ondo State, Nigeria

Abstract

Bitumen samples and soil samples around a bituminous deposit in Ondo State, Nigeria, were analysed for 40 K, 226 Ra and 232 Th employing gamma-ray spectrometry. The activity concentrations of 40 K, 226 Ra and 232 Th in soil varied from (45.2 ± 5.3) to (484.2 ± 25.9), BDL (below detectable limit) to (27.7 ± 2.1) and (22.8 ± 2.7) to (62.4 ± 6.8) Bq.kg-1 , respectively. The corresponding mean values were (240.2 ± 133.5), (13.3 ± 8.0) and (40.0 ± 10.2) Bq.kg-1 , respectively. The mean activity concentrations of the radionuclides in the bitumen were (58.4 ± 36.4), (16.1 ± 13.3) and (32.5 ± 13.1) Bq.kg-1 , respectively, for 40 K, 226 Ra and 232 Th. The mean absorbed dose and effective dose for the soil samples were (41.5 ± 8.9) nGy.h-1 and (50.7 ± 10.9) μSv.y-1 , respectively, while those of the bitumen samples were (29.5 ± 15.6) nGy.h-1 and (36.1 ± 19.1) μSv.y-1 , respectively. For radiological hazard assessment, the radium equivalent activity and the external hazard index were determined. The values of the radium equivalent activity and external hazard index obtained for the soil and bitumen samples were lower than the recommended limit.