Radioactivity concentrations and dose assessment for soil samples from wheat plantation areas of Narok County, Kenya
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Naturally occurring radioactivity has existed in our environment since the creation of the earth. Uranium, thorium and potassium radionuclides are relatively abundant in rocks and soils. Poor agricultural practices such as excessive use of fertilizers also lead to accumulation of radioactive elements in the soil. Due to their radiation, these radionuclides pose exposure risks which could lead to health related problems like cancer to the people exposed. There is therefore a growing concern on the health risks associated with such exposure to natural sources of radiation in our environment. In this research the activity concentrations of the natural radionuclides namely 238U, 232Th and 40K were measured for soil samples collected from different sites of Narok County wheat plantation area using NaI(Tl) gamma ray spectrometer. The mean values obtained are 52.3±4.2 Bqkg-1 , 61.3±3.9 Bqkg-1 and 1383.6±49.1 Bqkg-1 for 238U, 232Th and 40K respectively. It is observed that these values of 238U, 232Th and 40K are above the world average values. Radiological health hazard indices were evaluated using these values in standard analytical methods. The results showed that the mean value of radium equivalent activity is 246.5±9.6 Bqkg-1, while the values of absorbed dose rate (DR) and annual effective dose equivalent (HR) are 122.4±9.6 nGyh-1 and 0.60±0.03 mSvy-1 respectively. The values of external and internal health hazard indices are 0.66±0.03 and 0.81±0.04 respectively while the values of gamma and alpha indices are 0.94±0.03 and 0.26±0.02 respectively. All these values of hazard indices obtained are lower than their world permissible United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR) values for such environment. This shows that the risk due to radiation contamination in Narok county wheat plantation area is low.