ASSESSMENT OF RADIOLOGICAL HAZARD INDICES DUE TO NATURAL RADIONUCLIDES IN THE SOIL OF BITUMEN BELT OF ONDO STATE, NIGERIA
Abstract
This study investigates the natural radionuclide contents of soil samples collected from selected bitumen belt in Irele Local Government Area of Ondo State, Southwestern Nigeria. Fifteen soil samples were collected from Lola, Gbogi, and Ayadi. The measured activity concentrations of uranium-238, thorium-232, and potassium-40 across the samples varied from 13.50 ±1.91 to 31.69±2.47, 5.61±0.91 to 15.29±1.38 and 356.43±43 to 565.13±8.77 Bq/kg, respectively, with mean values of 23.28±1.43, 9.22±1.13, and 432.46±5.94 Bq/kg, respectively. The estimated absorbed dose rate from the soil samples ranged from 25.48 to 38.95 nGy/h, with an average value of 34.39 nGy/h. The annual effective dose for the soil samples varied from 0.0312 to 0.0478 mSv/y, with an average value of 0.042 mSv/y. The excess lifetime cancer risk ranged from 0.00109 to 0.00167, with an average of 0.00145. The radium equivalent range from 51.16 to 80.52 Bq/kg with an average value of 69.83Bq/kg.
The absorbed dose rate, annual effective dose, excess lifetime cancer risk and radium equivalent activity in the present study were lower than the average values. Therefore, this result obtained showed that the study area is free from radiological contamination.
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