Distribution of 40K, 238U and 232Th and associated radiological risks in river sand sediments across Enugu East, Nigeria

Abstract

The distributions of 40K, 238U and 232Th in sand sediments of rivers in Enugu east, Southeastern, Nigeria have been studied and measured using NaI(TI) gamma-ray spectrometry detector. The average activity concentrations of 40K, 238U and 232Th across the studied locations were found to range from 13.18 (at Emene river) to 109.64 Bqkg–1 (at Trans-Ekulu river), 8.52 (at Abakpa river) to 15.45 Bqkg–1 (Eke express river) and 10.67 (at Emene river) to 16.94 Bqkg–1(at Abakpa river), respectively. The overall averages were found to be 60.55, 12.07 and 13.02 Bqkg–1 for 40K, 238U and 232Th, respectively. The activity concentrations of the radionuclides in sediments of the study areas were found to be lower than their world average of 400, 35, and 30 Bqkg–1, respectively. Radium equivalent activity, external hazard index, internal hazard index, absorbed dose rate, total Annual effective dose, excess lifetime cancer risk and gamma representative index were calculated. The purpose was to assess the radiological suitability of the use of the sediments as building material. The overall average values of the radiological indices were 35.35 Bqkg–1, 0.10, 0.13, 15.96 nGyh–1, 0.10 mSvy–1, 0.34 × 10–3 and 0.25, respectively, which are lower than their respective recommended worldwide limits. The results of the study have shown that the radiation hazard associated with the use of these sediments is insignificant and therefore can be used for building construction purposes without restriction.