Ground radiometric mapping of Ondo State Nigeria using gamma ray spectrometry and geographic information system

The activity concentrations of U, Th and K in the soil samples of Ondo State, Nigeria, were determined using gamma spectrometry technique and the associated dose rates were calculated. The Kriging interpolation method was used to create the activity concentrations predictive maps of Ondo State with the aid of ArcGIS software. The validity of the predicted map values was established through validation and cross validation 238 processes. The activity concentrations ranged from 19.15±0.90 – 83.70±3.59 Bq/kg for U, 8.01±0.39 – 232 40 114.48±2.48 Bq/kg for Th and 2.75±0.13 – 501.98±24.56 for K. The absorbed dose rate was found to range -1 -1 from 39.39±0.21 to 177.24±5.23 nGyh with an average value of 90.94±3.13 nGyh . The predicted map obtained compares well with published values for the region. The root mean squared standardized errors 238 232 40 obtained were 1.021194, 1.024182 and 0.998373 for U, Th and K, respectively. These validated the appropriateness of the model used and the accuracy of the predicted values. Keywords: Soil, Radioactivity; Geographic Information Systems; Map; Gamma Ray Spectrometry