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

Abstract

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