Radiometric assessment of natural radioactivity levels of bituminous soil in Agbabu, southwest Nigeria

Activity concentrations of primordial radionuclides (226Ra, 232Th and 40K) in bituminous soil samples and viscous bitumen sample from Agbabu bitumen deposit, southwest Nigeria, has been measured using a high-resolution (HpGe detector) γγ-spectrometry. The average values of 226Ra, 232Th and 40K obtained are lower than the global average values. The Th/U activity ratio is comparable to values reported in literature. The average absorbed dose rate in outdoor air at a height of 1 m above the ground level was found to be 12.65±3.19nGyh-1, which is below the corresponding worldwide population weighted average value of 60nGyh-1. Both radium equivalent and representative level index values measured are lower than the internationally accepted limits for building and road construction materials. The results of the study indicate that the area has low background radiation level; as such no significant radiological hazard is expected in the area.