Investigation Of Natural Radioactivity Levels In Construction Rocks From Selected Quarries In Kericho County, Kenya Using Gamma-Ray Spectrometry

Abstract

The occurrence of naturally-occurring radionuclides, including Thorium-232, Uranium238, and Potassium-40, in various environmental matrices such as soil, water, rocks, and food, is the primary cause of exposure to ionizing radiation. Radionuclides possess the capability to induce deleterious effects on human health through inhalation, ingestion or crops consumption, leading to detrimental impacts on living cells or DNA of the body. Higher radiation doses cause mutagenesis, which results in lung cancer, pediatric leukemia, kidney damage and death. Through the use of Gamma-ray Spectrometric analysis, this study investigated the natural activity concentration levels of Potassium-40, Thorium-232, and Uranium-238 in construction rocks from the 15 selected quarries in the County of Kericho, Kenya. Based on the geological distribution of the rocks used in building, quarries from each sub-county were selected. To improve the representation and the quality of the data, two samples were taken from each quarry. From sample collection through preparation and measurement, IAEA protocols were followed. In order to attain secular equilibrium between Radium-226 and Thorium-232, samples were collected, crushed, oven dried (105 °C), weighed, and put in airtight containers and were then preserved for four weeks. The determination of radiological parameters, including specific activity concentration, radium equivalent, annual effective dose rate, absorbed dose rate, external hazard index, internal hazard index, and activity utilization index, was done to determine the extent of radiation exposure to various groups of people who were constantly in contact with rock fragments, such as miners, transporters, masons, residents of homes constructed from these rocks, and even the general public. 232Th, 238U, and 40K had average activity concentrations of 101± 5.08 Bq/kg, 56± 2.81 Bq/kg, and 1100 ±55.03 Bq/kg respectively and varied from 41± 2.07 to 138± 6.91 Bq/kg, 26 ±1.34 to 116 ±5.80 Bq/kg and 256±12.82 to 1919 ±95.99 Bq/kg respectively. The mean activity concentrations of 238U, 232Th, and 40K were more than the global average values of 50 Bq/kg, 50 Bq/kg and 500 Bq/kg respectively. The Absorbed Daose Rate was greater than the global recommended value of 60 nGy/h but lower than the permissible threshold value of 1500 nGy/h, ranging from 83± 4.16 nGy/h to 152± 7.60 nGy/h with an average value of 138 ±6.94 nGy/h. The mean effective dose rates for indoor and outdoor environments were 0.6 ±0.03 mSv/y and 0.1±0 mSv/y respectively and were below the 1 mSv/y global recommendation. The mean activity utilization, internal hazard, and external hazard indices were 2.1±0.1, 0.9±0.04 and 0.8±0.04 mSv/y respectively. The average Radium equivalent value of 285 ±14.28 Bq/kg, which was below the permissible limit of 370 Bq/kg and ranged from 165 ±8.25 Bq/kg to 309 ±15.47 Bq/kg, indicated that the excavated rocks for construction from the chosen quarries in Kericho county pose negligible health risks to those who are in constant contact with the rock fragments and the general public.