Gamma Ray Spectrometric Analysis of Sedimental Deposits at the Shores of Lake Nakuru, Kenya

Abstract

The main objective of this study was to assess human exposure to natural sources (U-238, Th-232 and K-40) of radiation on the shores of Lake Nakuru, Kenya. Gamma ray spectrometry of soil samples was done using NaI(Tl). The results obtained showed average activity concentrations of 36.9±9.1, 43.5±3.8 and 708±33.2 in Bqkg^-1 for ²³⁸U, ²³²Th and ⁴⁰K respectively. A total dose rate of 71.97 nGyh^-1, annual effective dose rate (outdoor) of 0.088 mSv and average hazard index of 0.410 were obtained. The average dose rate for the northern sector was found to be 96.22±5.39 nGy/h while the southern sector has 26.69±0.69 nGy/h showing enhanced pollution at the northern sector. The findings from this study showed that radiation hazard from terrestrial naturally occurring radionuclides is low and human radiation exposure is within safe levels. Spatial difference in the activity concentration between the northern and southern sectors of Lake Nakuru was observed. There is need to closely monitor the northern sector and the rivers discharging water there in order to establish the source of the elevated activity.

Keywords: Radionuclides, NaI(Tl) ?-ray Spectrometer, Activity concentration, Dose rate, Lake Nakuru