Radiation hazard in soil from Ajaokuta North-central Nigeria

Background: Measurement of the radiation dose distribution is important in assessing the health risk a population and serve as reference in documenting changes to environmental radioactivity in soil due to man-made activities. Materials and Methods: The activity concentration of 238U, 232Th and 40K in soil samples obtained from different locations in Ajaokuta Local Government area was measured using Hyper Pure germanium Detection System (HPGe). Results: The calculated average concentration of the radionuclides ranged from 12 ± 1 Bqkg-1 to 59 ± 2 Bqkg-1 for 238U, 14 ± 1 Bqkg-1 to 78 ± 5 Bqkg-1 for 232Th and 49 ± 2 Bqkg-1 to 1272 ± 23 Bqkg-1 for 40K. In order to evaluate the radiological hazards due to natural radionuclides within Ajaokuta, the absorbed dose rate, gamma index, radium equivalent and excess lifetime cancer risk were estimated. According to measured data from the top soil (0-10 cm), the estimated radium equivalent (Raeq) ranges from 55.7 Bqkg-1 at Steel Complex to 253.3 Bqkg-1 obtained from Forest samples. Conclusion: The mean absorbed dose rate, annual effective dose and gamma radiation index evaluated were 66.2 nGyh-1, 81.2 µSvy-1 and 1.05 respectively which are higher than the recommended limit for normal background radiation. Thus, we conclude that people living in these locations may be exposed to higher radiation.