Investigation of Radiation Levels in Soil Samples Collected from Selected Locations in Ogun State, Nigeria

Present study measured the terrestrial radiation and evaluated absorbed dose rates from primordial radionuclides ²³⁸U, ⁴⁰K and ²³²Th in sixty soil samples collected from north, west, east and south of Ewekoro cement factory premises, Owowo village situated adjacent to the factory and Covenant University, Ogun State using the gamma ray spectrometry method. The gamma absorbed rate and annual effective dose equivalent were calculated so as to estimate the hazard index of the primordial radionuclides. Measured concentrations of radionuclides in Ewekoro cement factory soils were as follow: [²³²U {1.60 ± 1.60 Bqkg⁻¹ (east) - 2.56 ± 0.08 Bqkg⁻¹ (north)}, ²³²Th {44.78 ± 1.83 Bqkg⁻¹ (east) - 56.62 ± 1.96 Bqkg⁻¹ (north)}, ⁴⁰K {261.54 ± 12.67 Bqkg⁻¹ (south) - 342.08 ± 14.17 Bqkg⁻¹ (east)}] and Owowo village [²³²U {1.78 ± 0.09 Bqkg⁻¹ (east) - 2.62 ± 0.08 Bqkg⁻¹ (north)}, ²³²Th {50.07 ± 1.93 Bqkg⁻¹ (west) - 61.69 ± 1.89 Bqkg⁻¹ (north)}, ⁴⁰K {244.11 ± 13.38 Bqkg⁻¹ (north) - 296.40 ± 14.90 Bqkg⁻¹ (south)}]. These locations have higher concentration of all radionuclides than that of Covenant University soils, which are as follows: [²³²U {0.62 ± 0.07 Bqkg⁻¹ (south) - 1.07 ± 0.06 Bqkg⁻¹ (north)}, ²³²Th {30.23 ± 1.87 Bqkg⁻¹ (south) - 38.87 ± 1.78 Bqkg⁻¹ (east)}, ⁴⁰K {243.35 ± 12.57 Bqkg⁻¹ (south) - 301.15 ± 13.55 Bqkg⁻¹ (north)}]. The mean absorbed dose and annual equivalent effective dose is 40.88 nGyr^-1 and 0.05 mSv respectively. The study found that the activity concentrations and radiological hazard index from samples from Ewekoro and the neighbourhood are consistently higher than those from Covenant University however; the values are less than the recommended safe levels.