Effects of Seasonal Change on the Levels of Geogenic Radionuclides in Sand and Rocks from Tyaa River deposit in Kitui County

Abstract

The average activity concentration of 226Ra, 232Th and 40K in rock samples during the rainy season was 22±1.1 BqKg-1, 46±2.3 BqKg-1, and 659±33 BqKg-1 respectively, while in the sand was 27±1.4 BqKg-1, 49±2.5 BqKg-1and 824±41 BqKg-1 for 226Ra, 232Th and 40K respectively. A repeat study during dry season reported higher activities for 226Ra, 232Th, and 40K for most samples. The corresponding dose rates and radiological indices estimated from specific activities of 226Ra, 232Th and 40K showed an upward trend as seasons changed from rainy to dry. Both seasons reported radiation doses below the permissible limits.