Pore structure and radon emission characteristics of shallow soil in the Golmud River Basin of the Qinghai‒Tibet Plateau

The Qinghai-Tibet Plateau (QTP) has a high altitude, strong radiation and wide distribution of frozen soil, with typical alpine soil. Investigating the radon exhalation level of this distinctive soil is crucial for assessing the human settlement environment in the region. This study takes the Golmud River Basin as a case to study the pore structure and radon emission characteristics of shallow soil in a typical QTP area. Furthermore, explored the correlation between terrain, altitude, depth, and pore structure with radon emission rate. The key findings are as follows: In areas with severe salinization, soil exhibit the largest specific surface area and total pore volume, the mean values were 20.07 cm²/g and 0.05 cm³/g, respectively. As altitude increased, the specific surface area, total pore volume, and macropore fractal dimension D_a gradually rose, accompanied by significant expansion in macropore diameter. Soil at depths less than 20 cm demonstrated smaller specific surface area, total pore volume, and D_a. Conversely, depths exceeding 20 cm exhibited significantly larger specific surface area and total pore volume, albeit with a tendency for these metrics to decrease with increasing depth. Radon exhalation rate generally increased with burial depth and elevation. Notably, soil radon exhalation rate exhibited a positive correlation with micropore content and total pore content, with a stronger correlation observed with total porosity. While the source area displayed higher radon exhalation rates compared to the deposition area, the overall soil radon exhalation rate in the QTP was relatively lower than other global regions, the maximum is only 0.42 × 10⁻³ Bq/g·h. These research outcomes offer valuable insights for soil radiation risk assessment in the QTP.