Measurement of outdoor terrestrial gamma radiation in the Sultanate of Oman

The terrestrial gamma radiation level was determined throughout the Sultanate of Oman over a 3-y period. The dose rate at 1 m above the ground was measured at 512 locations using a compensated Geiger-Muller detector. The activity concentration of soil/rock samples, collected from 112 locations, was determined by gamma spectrometry. Dose rates calculated from the activity concentrations compared well with the measured values corrected for the cosmic ray contribution. Some of the highest terrestrial dose rates, up to 110 nGy h(-1), were measured in shales (Wadi Bani Awf, Saih Hatat, and the Huqf) and exposed basement granites (Jebal Jalan and the Mirbat peninsula). Two small hot spots were found where the maximum dose rate was 1,024 nGy h(-1). The average dose rate in the main population area of the Batinah is 38.5 nGy h(-1) (0.29 mSv y(-1)) and Muscat 44.9 nGy h(-1) (0.34 mSv y(-1)). The mean population weighted dose rate is 39.8 nGy h(-1) (0.30 mSv y(-1)). Most of Oman's surface rock is limestone, which is low in concentrations of radionuclides from the uranium and thorium series. Hence, the average dose rate is well below the world average of 0.45 mSv y(-1).