Natural Radionuclide Concentrations and Radiological Impact Assessment of Soil and Water in Tanke-Ilorin, Nigeria

Abstract

Radioactivity measurement of water and soil samples from Tanke-Ilorin, Nigeria was carried out using a thallium activated Canberra vertical high purity 3˝×3˝ Sodium iodide [NaI(TI)] detector connected to ORTEC 456 amplifier. The results were used to estimate all the radiological impact parameters in order to effectively ascertain the level of the radiological health hazard to Human life by the use of such materials in that area. The mean Absorbed Dose Rate for the soil and water samples was found to be 59.45 and 8.33 nGy/h. The estimated mean Annual Effective Dose (AED) for the ingested radionuclide in drinking water from the area for infants, 1year, 5 years, 10 years, 15years and adult were 1.9395, 2.0087, 1.2487, 0.9009, 0.7019, and 1.1688 mSv/y respectively. This reveals that children within 1year are more susceptible to radiation hazards in the area followed by the infants, 5 years, adults, 10 years and then 15 years respectively. The mean AEDoutdoor for the soil is 0.07291 mSv/y and mean AEDindoor is 0.29165 mSv/y. These mean values are within the safe limit of 1mSv/y for the general public. The mean Raeq for the soil and water samples is 114.50 Bq/kg and 17.53 Bq/l respectively. These estimated average values were lower than the recommended maximum value of 370 Bq/kg. The estimated hazard indices Hin and Hext for the soil is 0.35 and 0.31 respectively. While that of water is 0.065 and 0.047. These values of Hin and Hext in soil and water are less than unity which follows that hazardous effects of these radionuclides and their short-lived progenies are negligible. The estimated Excess Lifetime Cancer Risk (ELCR) for the soil and water samples is 1.02078 x 10-3 and 0.14301 x 10-3 . The estimated value of ELCR for soil is high which implies that the probability of developing cancer over a lifetime considering seventy years as the average life span of humans is high. The estimated mean values for the Annual Gonadal Equivalent Dose (AGED) in the soil and water is 0.43797 mSv/y and 0.05844 mSv/y. The estimated mean Iγ for the soil and water samples was 0.9410 mSv/y and 0.1297 mSv/y respectively. These values are within the safe limit of less than the universal standard of unity. The results showed trends that are generally low for most of the radiological impact parameters calculated except for few indices whose values are above the UNSCEAR recommended thresholds. Therefore, there may be no serious immediate radiological effects to the populace in this area.