Evaluation of natural radioactivity in selected soil samples collected from northern regions of Oman

Abstract

This study explores the radioactivity concentration in soil in the Northern regions of Oman. The naturally occurring radioactive nuclides of the main series, 238U, 232Th, 235U and 40K and artificial radionuclide 137Cs have been studied by means of low level gamma spectroscopy. Majority of the studied valleys (wadis) are descending from Super Hajar Mountains either towards its east part (coastal area) or the west part (desert). Soil samples were collected from headwaters and estuaries of wadis where residences and agriculture activities exist. In soil samples, the results showed that 238U radionuclide was presented in concentrations of the range (4.5 – 24.0) Bq.kg−1while 232Th was found in the range (2.4-20.6) Bq.kg−1. Ranges of 235U and 40K were reported as (0.6-2.5) Bq.kg−1 and (47-296) Bq.kg−1 respectively. Artificial radionuclide 137Cs was found in all soil samples in the range (2.8-11.9) Bq.kg−1. The hazard parameters, dose rate (D), annual effective dose (HR), equivalent radium activity (Raeq), internal hazard index (Hin), external hazard index (Hex) and gamma representative level index (Iγr) were all calculated. The values of D, HR and Raeq were found in the ranges (6.6-33.5) nGy/h, (0.8-4.1)*10−2 mSv/yr and (17.2-88.6) Bq.kg−1 respectively. The values of Hin, Hex and Iγr were all less than 1. These obtained results remained below the optimum admissible values according to UNSCEAR.. The results indicate that the radiation hazard from naturally and artificially radionuclides in soil samples from the area studied in this current work is not significant.