Abstract: The analysis of Naturally Occurring Radionuclides (40k, 226Ra and 228Ra) has been carried out in soil samples collected from Oil Mining Lease (OML) 58 and 61 (Oil and Gas Producing Areas) in the Niger Delta Region of Nigeria, using gamma spectroscopy operated on a Canberra vertical high purity coaxial germanium (HpGe) crystal detector. The Activity concentration of the samples ranged from 98.84 18.95 Bqkg-1 to 205.98 29.06 Bqkg-1 with mean value of 148.10 30.36 Bqkg-1 for 40K, 11.93 3.92 Bqkg-1 to 15.41 6.02 Bqkg-1 with Mean value of 13.28 4.67 Bqkg-1 for 226Ra, 9.36 3.63 Bqkg-1 to 14.05 5.12 Bqkg-1 with mean value of 11.11 4.13 Bqkg-1 for 228Ra. These values obtained are well within the world ranged and values reported elsewhere in other countries. The External Hazard Index (Hex) ranged from 0.089 to 0.125 with a mean of 0.107, the internal hazard Index (Hin) ranged from 0.121 to 0.165 with a mean of 0.142 respectively. The Radium equivalent activity (Raeq) calculated ranged from 35.01 Bqkg-1 to 46.56 Bqkg-1 with a mean of 40.57 Bqkg-1. The Absorbed dose ranged from 15.44nGyh-1 to 22.44nGyh-1 with a mean of 19.30nGyh-1, while the Effective dose ranged from 0.019 mSvy-1 to 0.027mSvy-1 with a mean of 0.023mSvy-1. These calculated hazard indices are used to estimate the potential radiological health risk in soil and the dose rate associated with it are well below their permissible limit. The soil from the study area provides no excessive exposures for inhabitants and can be used as construction materials and agricultural purposes without posing any immediate radiological threat to the public. However, inhabitants are cautioned against excess exposure to avoid future accumulative dose of these radiations especially from other sources.
Keywords: Soil, Assessment, Gamma-Spectroscopy, hazard Indices