Study on the effect of soil type and pore structure on radon release from soils in coal mine areas

Radon release rate is one of the most important indicators to assess the environmental radon hazard. In the loess-covered area of northern China, the decay of uranium ore associated with the coal seams has caused elevated radon concentrations in overlying soil layers, significantly increasing the risk of various respiratory diseases to residents. In this paper, the effects of burial depth and soil type on radon release rate were investigated by X-ray diffraction (XRD) analysis, low-temperature nitrogen adsorption (LTNA) experiments, and measurement of radon concentrations in the soil based on the pore structure characteristics of soil layers. The results showed that all N₂ adsorption isotherms in the soil were inverse-S shaped with well-developed mesopores. The number of mesoporous materials was positively correlated with the radon release rate of the soil. The overall tendency of the radon release rate was to firstly increase and then decrease with increasing depth. The relative degree of variation in radon exhalation rate between adjacent soil layers was in the order as follows: red clay > paleosoil > loess > pedocal. The results of this study can help to understand the release pattern of radon in different soils and provide valuable references in reflecting the characteristics of radon release in regional soils.