Baseline Radionuclide Distribution Patterns in Soil and Radiation Hazard Indices for Abak, Nigeria

A gamma spectroscopy analysis for the naturally occurring radionuclides 226 Ra, 232 Th and 40 K has been carried out for soil samples collected from communities in Abak Local Government Area of Akwa Ibom State to determine the concentration and distribution patterns of these radionuclides in the study area and to assess the possible radiological risks from the soil. The activity concentration of the samples range from 14.80±1.16Bq/kg to 150.20±11.47Bq/kg with a mean value of 98.709±7.693Bq/kg for 40 K; from 14.52±3.49Bq/kg to 42.04±8.59Bq/kg for 238 U with a mean of 24.826±5.425Bq/kg and from 3.05±0.27Bq/kg to 7.00±0.58Bq/kg with a mean of 5.172±0.31Bq/kg for 232 Th. These values are within international regulatory standards. Assessment of the radiation hazard levels for the area gave values of 18.789±3.102nGy/h for absorbed dose, 0.3±0.05Bq/kg for representative level index, 39.82±6.65Bq/kg for radium equivalent, 0.11±0.02 for external hazard index, 0.18±0.032 for internal hazard index and 0.023±0.004mS/yr for effective dose rate. These indices are much lower than the ICRP permissible limits for soil showing that the soil of the study area poses no radiological threats to the public. Keywords : Radionuclide concentration, radiation hazard index, radium equivalent, internal hazard index