Assessment of exhalation rates of radon and thoron in soil from the Jaunsar-Bawar region of the Indian Himalayas

This research investigates exhalation rates of radon (222Rn) and thoron (220Rn) from soil samples in the Jaunsar-Bawar region of the Indian Himalayas. Before sampling, gamma radiation rates were evaluated, ranging from 0.08 to 0.33 µSv/h. The observed 222Rn mass exhalation rates range between 3.56 and 82.08 mBq/kg/h, with an average of 25.67 mBq/kg/h. Additionally, the surface exhalation rate of 220Rn varies from 1.28 to 22.69 Bq/m2/s, averaging 7.90 Bq/m2/s. Projected 220Rn mass emission rates span 154–2356 mBq/kg/s, with a mean of 939 mBq/kg/s. The dataset analysis employs best-fit statistics, revealing the Weibull distribution as the optimal model for gamma dose rate and 220Rn mass emanation rates. Lognormal distribution suits 222Rn mass exhalation rates, and the Gamma distribution excels for 220Rn surface exhalation rates, aligning with log-likelihood estimator indications.