Effects of seasonal change on the levels of geogenic radionuclides in sand and rocks from Tyaa river deposit in kitui county

Abstract

A total of 56 samples of raw building materials (26 rocks and 30 sand samples) each weighing 500g were randomly sampled along the riverine for the alternate rainy and dry seasons. Gamma-ray spectrometric analysis of rocks sampled during the rainy season reports an average activity concentration of 226Ra, 232Th and 40K of 22±1.1 BqKg-1, 46±2.3 BqKg-1, and 659±33 BqKg-1 respectively, while the sand collected during the same season revealed a mean activity of 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. However, both seasons reported radiation doses below the permissible limits.