Assessment of specific activity concentration and percentage contribution of 226Ra, 232Th and 40K to absorbed dose rate of the Port Harcourt Refinery Company host community
survey of radioactivity concentration in soil and water from the Port Harcourt refinery company host community was carried out using the gamma ray spectrometer with NaI(TI) detector to determine the concentration of the primordial radionuclides 226Ra, 232Th and 40K. 20 samples (10 each of soil and water) were collected at random from various parts of the community. The mean specific activity obtained for 40K was 76.64 ± 22.93 Bq kg-1(soil),with a range of 41.54 ± 14.80- 175.54 ± 39.53Bqkg–1 and 58.88 ± 21.66 Bq l-1 (water) with a range of 36.09 ± 14.06-121.18 ±28.75Bq l-1. For 226Ra (soil), the mean specific activity was 7.43 ± 3.47 Bq kg-1 with a range of 6.62 ± 2.24–10.10 ± 4.16Bq Kg–1 and 4.16 ± 1.97Bq l-1 (water) with a range of 2.61 ± 1.23- 5.46 ± 1.66Bq l-1 and the mean specific activity for 232Th(soil) was 4.71 ± 2.46 Bq kg-1 with a range of 3.25 ± 2.10 - 6.26 ± 4.01Bqkg–1 and 3.30 ± 1.90 Bq l-1 (water )with a range of 2.46 ± 2.08-4.16 ± 2.07Bq l-1. The radionuclide concentrations in the soil are all lower than the ICRP standards, while those for the water samples are significantly higher (six times for 40K; eight times for 226Ra and 15 times for 232Th).The percentage contribution of each radionuclide to absorbed dose rate in soil and water were also determined. The absorbed dose rates calculated for both samples vary between 24.60 to 79.74nGy/hr in soil and 18.52 to 54.98 nGy/hr in water. The results of this work indicate that effluents from the refinery have had some impact on the radionuclide concentration of the water of its host community.
Keywords: Radionuclide concentration, specific activity, absorbed dose rate, refinery effluent, Gamma spectrometry