Gamma Ray Spectroscopic Analysis Of Soil And Green Tea Leaves Of Kericho County

ABSTRACT

The knowledge of the distribution of the radionuclides and their levels in the environment is paramount in assessing the effects of radiation exposure from either terrestrial or extraterrestrial sources. Human population and other living organisms are exposed to radiation from naturally occurring radionuclides in soil, building materials, food, volcanic eruptions and other environmental materials. Natural background is of terrestrial and extraterrestrial origin. Terrestrial sources originate from primordial radionuclides in the earth’s crust and extraterrestrial radiations originate as cosmic rays from outer space, natural and artificial radioisotopes and in granite rocks. This study is aimed at determining the concentration of radionuclides in Kericho County using both Kericho tea estate and Mau complex samples. Samples of both soil and green tea leaves were collected, prepared and analyzed in the laboratory using NaI (Tl) gamma ray spectrometer to determine the activity concentrations of primordial40K, 238U and 232Th. Some samples from Mau complex were also collected, prepared and analyzed so that the activity concentrations of40K, 238U and 232Th radionuclides can be compared with those of the Kericho samples. The results obtained registered an average activity concentration of 66±8 Bqkg-1 for 238U, 55±2 Bqkg-1 for 232Th and 819±9 Bqkg-1 for 40K for Kericho tea estate soil, 51±5 Bqkg-1 for 238U, 51±4 Bqkg-1 for 232Th and 724±9 Bqkg-1 for 40K for Mau soil, 48±5 Bqkg-1 for 238U, 43±2 Bqkg-1 for 232Th and 667±8 Bqkg -1 tea leaves and53±3 Bqkg-1 for 238U, 40±4 Bqkg-1 for 232Th and 558±7 Bqkg-1 for 40K for Mau leaves. An annual effective dose rate (outdoor) of 0.12±0.06 mSvy-1 and 0.09±0.005 mSvy-1 was obtained for both soil and tea leaves respectively which is lower than the safety limit to public exposure of 1mSvy-1 . Comparisons of the activity concentration in the two ecosystems show that, the Kericho tea estate environment is more polluted than the Mau environment and this could be attributed to more human activities taking place in the tea industry that can result in environmental pollution as opposed to Mau environment.