Study on the response of radon gas release in permafrost areas to temperature changes

A model of frozen soil radon release under thermal-hydro coupling was established and verified by experiments to evaluate the risk of soil radon release in cold regions aggravated by permafrost degradation under climate change. The model and experimental results show that during the warming process of frozen soil (- 30 °C to 0 °C), the soil radon concentration (< 20,000 Bq/m³) or radon exhalation rate (< 0.05 Bq/(m² s)) in some cold regions (e.g., Northeast China, Russia, Sweden, and Canada) is generally lower than the thresholds specified in China's Code for Indoor Environmental Pollution Control of Civil Building Engineering (GB 50325-2020). Consequently, additional protective measures are generally unnecessary in these areas. However, in a few regions (e.g., Norway) with high background levels of soil radium specific activity, permafrost degradation may cause their radon release levels to exceed the safety threshold, endangering human health. In addition, the model established in this study provides an effective tool for assessing the cumulative risk of radon concentration in confined spaces in cold regions. It can also predict the worst-case scenarios of radon exposure in poorly ventilated buildings, offering a scientific basis for developing radon risk warning and protection strategies in cold regions.