Assessment of radionuclide concentration with depth in lithology of Port Harcourt, Nigeria

Abstract

A survey of the Radionuclide concentration with depth in the lithology of Obio-Akpor Local Government of Rivers State was carried out. Samples were collected at 5m interval from 3 wells (randomly selected). The gamma radionuclide concentrations of the samples were measured using a well calibrated thalium-activated Sodium Iodide detector NaI(Tl). The average specific activity values obtained were 318.9 Bqkg^-1, 285.7 Bqkg^-1 and 256.7 Bqkg^-1 for well 1, well 2 and well 3 respectively for K-40 radioisotope; 15.5 Bqkg^-1, 13.8 Bqkg^-1 and 15.7 Bqkg^-1 for well 1, well 2 and well 3 respectively for Ra-226 radioisotope; and 11.9 Bqkg^-1, 11.5 Bqkg^-1 and 10.6 Bqkg-1 for well 1, well 2 and well 3 respectively for Th-232 radioisotope. Also, the Absorbed Dose rate and the Equivalent Dose Rate were calculated and an average of 27.5nGy/hr and 0.2mSv/yr were obtained for well 1, 25.6nGy/hr and 0.2mSv/yr for well 2 and 25.9nGy/hr and 0.2mSv/yr for well 3. These obtained values were less than the international standards of 55nGy/hr and 0.7mSv/yr for Absorbed Dose rate and the Equivalent Dose Rate respectively. The results indicate that the radiation level within the sampled areas may pose no significant health-side effect on the populace. Also, it was observed that radionuclide concentration reduced with depth.

Key Words: lithology, radionuclides, activity concentration, absorbed dose, equivalent dose