Correlations of 226Ra and 222Rn activity concentrations in surface soil and groundwater of basement complex geological area of southwest Nigeria

The quantitative evaluations of naturally occurring radioisotopes in environmental media have provided significant information on the geological and radiological characteristics of different environments around the world. In furtherance to a preliminary study within southwest Nigeria set out to determine the distribution of Rn-222 in groundwater and soil gas, the present study employed a well-shielded NaI(Tl) and RAD 7 detectors to determine activity concentrations of Ra-226 and Rn-222 in the media. Samples were collected from 100 sampling sites spatially distributed within the study area. Multivariate statistics were employed to extract the relationships between the activity concentrations of Ra-226 and Rn-222 in order to ascertain their origin and behavior in the basement complex geological area of southwest Nigeria. The mean activity concentration of Ra-226 falls below the world average value of 35 Bq kg(-1) in soil as reported by UNSCEAR, and Rn-222 mean activity concentration is lower than 100 Bq l(-1) recommended by WHO and European Commission as the criterion level in utility water for the members of the public. It can therefore be concluded that there is no significant radiological risks to the environment and human health due the presence of the measured radionuclides in soil and groundwater.