Spatial Distribution of Radiometric and Dosimetric Parameters in Soil Samples from Selected Areas in Bayelsa State, Nigeria

Abstract

Radiation from radioactive materials/radionuclides in the environment enhanced by anthropogenic activities is presently of a great concern globally. The objective of this study is to determine the radiometric and dosimetric parameters from soil samples collected randomly from the study area of Bayelsa State, Nigeria. The samples were prepared using standard methods and analyzed with a high resolution Hyperpure Germanium Detector configuration (HPGe). The results showed the clay samples to have higher activity concentration to the sands samples with activity concentration of clay samples ranging between 68.99±9.05 –189, 42±21.11Bq/kg and the sand samples with activity concentration range of 17.95±5.87 – 38.59±7.43Bq/kg. The activity concentration spatial distribution map in clay lithologies showed 2 peak values trending north-west, while the sand lithology showed a single peak central distribution. The result also showed the values of the absorbed doses with the 8 clay samples values ranging between 59.09 - 155.25nGy/h and sand samples values between 17.90 – 33.92nGy/h. The spatial distribution of the dose showed 2 peak central distribution in clay samples and north-east trending distribution of high peak values for samples with sand lithologies.  In addition, the results showed an effective absorbed dose of range of 0.235-0.0616mSv/y for samples with clay lithology and 0.0071-0.0135mSv/y for samples with sand lithology The activity concentration of all the samples studied are below the 1000Bq/kg international reference limit  for Radium 226, Thorium 232, uranium 238 and 10,000Bq/kg for potassium 40. The absorbed dose rate and annual effective absorbed dose are also below the international reference limits published by ICRP, 2007 and UNSCEAR, 2000 publications. Also, effective activity maximum limit of 370Bq/kg for input raw materials for public building is not exceeded.