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.