Assessment of Natural Radioactivity and Associated Dose Rates in Surface Soils

What is it about?

Assessment of natural radioactivity and associated dose rates of surface soils in Oluwa Glass industry environment of Igbokoda, Ondo state, Nigeria was carried out by means of well-calibrated NaI(TI) that was well shielded with a detector coupled to a computer resident quantum MCA2100R multichannel analyzer with an aim to measure the concentrations of 40K,238U and 232Th radionuclides in the soil samples; estimate the absorbed dose rate, annual effective dose and excess lifetime cancer risk in the study area. The activity concentrations in the soil samples were found to range from 153.74 to 228.13 Bq kg-1 with a mean value of 194.69± 17.40 Bq kg-1 for 40K, from 9.40 to 14.07 Bq kg-1 with a mean of 11.49 ±2.10 Bq kg-1 for 238U and from 8.42 to 12.08 Bq kg-1 with a mean value of 9.94 ± 1.05 for 232Th respectively. The mean absorbed dose rate was 19.73 ± 18.43 nGyh-1, the annual effective dose was 24.20 ± 8.31 µSvy -1 and the excess lifetime cancer risk was 0.085. The activity concentration of 40K reported in the present study was higher than the value of 58.69 Bq kg-1 for 40K reported for soil samples collected from parts of Sagamu, Southwestern, Nigeria. The mean absorbed dose rate, mean annual effective dose and mean excess lifetime cancer risk reported in this present study were lower than the world average values of 54.00 nGyh-1, 66.00 μSvy-1 and 0.29 respectively. Thus, it can be deduced from our results, that 40K, 238U and 232Th naturally occurring radionuclides, to a very great extent, had already decayed to stable nuclei as at the time of carrying out this research on the chosen site at Igbokoda, Ondo State, Nigeria.

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Why is it important?

Oluwa Glass Industry located at Igbokoda area of Ondo State is a typical example of the United Nation Nuclear Regulatory Commission identified problem of artificial sources of radiation exposure to human cited above. Oluwa Glass Industry is owned by the Ondo State Government in Nigeria and has been temporarily shut down due to financial mismanagement. Glass production is known to involves extensive usage of ionizing radiation, there may be improper handling of gauge sources, spillage and release of radioactive materials from pressurized system, unauthorized disposal of waste, emergency and natural disasters, fire, explosion and transportation accidents which are some of the potential contamination channels that can lead to extremely large internal or external radiation doses to the exposed individual of the public. Of recent, the study area and its environs are basically used for farming, since the abandonment of glass productions.

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