Assessment of exhalation rates of the soil and dispersed radon in groundwater in the Bengaluru district.

This study investigates radon and thoron exhalation from soil, along with radon and radium concentrations in groundwater, across 23 sampling locations in Bengaluru, Karnataka, India, using a scintillation-based Smart RnDuo detector. Radon mass exhalation rates ranged between 17 ± 1.3 and 91.1 ± 4.7 mBq/kg/h, with a mean of 37.7 ± 2.1 mBq/kg/h, below the reported global average. In contrast, thoron exhalation rates ranged from 1755 ± 193 to 8410 ± 409 mBq/m2/s, with a mean of 4126.23.83 ± 278.52 mBq/m2/s, exceeding the global average. Groundwater radon concentrations varied from 9.4 ± 1.4 to 219.0 ± 5.5 Bq/L, yielding an arithmetic mean of 91.4 Bq/L and a geometric mean of 75.3 Bq/L; several sites approached or exceeded the WHO guideline threshold of 100 Bq/L. Gamma radiation levels averaged 179.7 nSv/h, above the Indian baseline but corresponding to an annual effective dose of 440.9 μSv/y, which remains below the ICRP public dose limit of 1 mSv/y. These findings underscore the influence of local hydrogeological conditions and soil characteristics on radon variability and highlight the need for continued monitoring and mitigation strategies in groundwater-dependent communities.