Radiometric and radon exhalation rate analysis of Gahirat marble, Chitral Khyber Pakhtunkhwa, Pakistan

Abstract

Background : Geological materials usually contain trace amounts of radioactive materials and may serve as a natural source of background radiation exposure to the general public. This study presents results of radiometric and radon exhalation rate (RER) analysis of 28, export quality marble samples taken from various quarries of Gahirat Chitral area. Materials and Methods : The marble specimens were investigated using gamma spectroscopy by HPGe detector. Samples were also analyzed for radon exhalation rate using closed CAN technique. Results and Discussion : The mean values of 226 Ra, 232 Th and 40 K were found as 31.598 ± 0.989, 1.529 ± 0.308 and 5.273 ± 1.593Bqkg - 1 respectively. Average value of Ra eq was estimated as 34.19±1.55 Bqkg - 1 . Radiation risk parameters viz. internal (H in ), external (H ex ), alpha (I α ) and gamma (I γ ) hazard indices were estimated and found less than unity value. The values for effective indoor (Ḋ in ) and outdoor gamma dose rates (Ḋ out ) due to the contents of primordial radionuclides were also estimated. The contribution of radon towards radiation exposure was assessed by estimating RER, which was found in the range (1.01±0.07 to 9.67±0.27) ×10 - 2 Bqm - 2 h - 1 with mean value of (5.84±0.002) ×10 - 2 Bqm - 2 h - 1 . Conclusion : The surface radon exhalation rate values estimated in the current study were found smaller than as reported for many other countries. The results obtained for gamma emitting radionuclides have been compared with the data available in the literature. Measurements shows that marble samples investigated have low concentrations of radionuclides and uses of marbles in dwellings do not pose significant threat to the inhabitants.