Investigation of Natural Gamma Radioactivity Levels and Associated Dose Rates from Surface Soils in Ore Metropolis, Ondo State, Nigeria

Natural radioactive materials under certain conditions can reach hazardous radiological levels. Therefore, it becomes necessary to study the natural radioactivity levels in soil to assess the dose to the population in order to determine the health risks and to obtain a baseline for future changes that may occur due to human activities. The motivation for this study was the devastating civil war that took place in Nigeria from 1967 to 1970, in which the study area was one of the battle fields. The results of our investigations of the soil in the metropolis of Ore show that the activity concentrations of 226Ra, 232Th and 40K in the soil vary from 14.21±1.40 to 25.87±1.01Bq/kg; 5.30±1.00 to 20.99±1.10Bq/kg and 58.01±1.80 to 382.98±3.00Bq/kg respectively. The total absorbed dose rate calculated from the activity concentrations of 226Ra, 232Th and 40K ranged from 15.42±1.10 to 40.99±1.36 nGy/h. The radium equivalent activity (Req) and the annual effective dose rates were also calculated and found to vary from 33.39±2.44 to 85.07±2.96 Bq/kg and from 18.91±1.35 to 50.27±1.69 µSv/y respectively. These values were found to be within the same range as recommended values (UNSCEAR, 2000). The study also indicated that 137Cs detected at three locations is an indication of the presence of artificia