Radiological hazard assessment of natural radionuclides in soils of some oil-producing areas in Nigeria

Abstract

ABSTRACTThe activity concentrations of 226Ra, 232Th, and 40K were measured in soil core samples collected from eight locations with untapped crude oil deposits and two oil fields where crude oil exploration is ongoing in Nigeria. Measurement was carried out using a high-purity germanium (HPGe) detector. The radiological hazard to humans due to the radiation emitted from natural radionuclides in soils collected from the areas studied was assessed. In areas with untapped crude oil deposits, the average values of the absorbed dose rate (D), annual effective dose equivalent (AEDE), radium equivalent activity (Raeq), annual gonadal dose equivalent (AGED), external hazard index (Hex), internal hazard index (Hin), representative gamma index (Iγ), and excess lifetime cancer risk (ELCR) were 11.40 nGy h−1, 13.98 µSv y−1, 23.39 Bq kg−1, 82.41 mSv y−1, 0.063, 0.076, 0.183, and 0.049 respectively. In areas where crude oil exploration is ongoing, the average values of D, AEDE, Raeq, AGED, Hex, Hin, Iγ, and ELCR were 29.42 nGy h−1, 59.53 µSv y−1, 59.60 Bq kg−1, 206.69 mSv y−1, 0.162, 0.203, 0.455, and 0.209, respectively for workers who spend up to 8 hours per day at the oil fields. For workers who spend 10 hours per day at the oil fields, the average values of the AEDE and ECLR were 75.76 µSv y−1 and 0.266, respectively. Although all the calculated radiation hazard indices are lower than the permissible limits set by ICRP, the values are higher in areas where crude oil exploration is ongoing than areas with untapped crude oil deposits. This shows that oil and gas exploration activities have impacted negatively on the radiological status of the environment of the study area.