Bitumen samples and soil samples around a bituminous deposit in Ondo State, Nigeria, were
analysed for 40K, 226Ra and 232Th employing gamma-ray
spectrometry. The activity concentrations of 40K, 226Ra and
232Th 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 40K, 226Ra and
232Th. 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.