降雨对土壤氡浓度影响的理论模拟与实验研究

doi:10.27045/j.1000-8187.202605004

摘要/Abstract

摘要： 为揭示降雨对土壤氡浓度的影响规律及其机理,本文采用实验观测与数值模拟相结合的方法,系统研究了降雨条件下土壤氡浓度的动态响应特征。开展了不同降雨模式的跟踪测量实验,持续监测了降雨量、土壤氡浓度、土壤气体渗透率等参数的动态变化,提出了由孔隙抑制、射气衰减效应、盖层效应及降雨渗流效应四种机制共同作用的土壤氡浓度理论假设,构建了两层土壤水-气氡运移模型,实现了对降雨入渗过程中氡浓度场的理论模拟。研究结果表明:两层土壤模型所构建的四种机制耦合模型可重现降雨实验中土壤氡浓度先升后降的响应趋势;94%的模型预测值落入实测值的±2σ区间,接近正态分布2σ置信水平的理论覆盖率(95.4%)。归一化分析表明,盖层效应参数是四种机制中对含水量变化最敏感的参数;入渗对流速度在达到峰值后下降,揭示了高含水量下气相通道消失导致的对流上限效应。随着降雨总量由64 mm增至227 mm,模拟偏差由氡浓度上升滞后逐渐转为系统性偏低,平均绝对误差(MAE)由1.96上升至3.81 kBq/m³,反映出模型对暴雨期盖层效应所导致的地表封闭与氡积累机制表达尚不充分,四种机制耦合的瞬态响应幅度仍有改进空间。研究结果可为排除降雨干扰、提高土壤氡浓度在氡地质潜势评价及铀矿地质勘查氡数据处理中的应用提供理论依据。

关键词: 土壤氡, 降雨, 含水量, 两层土壤模型

Abstract: To reveal the influence law and mechanism of rainfall on soil radon concentration, this study combined with experimental observation and numerical simulation to research the dynamic response characteristics of soil radon concentration under rainfall conditions. Real-time observation under different rainfall were carried out, and the dynamic changes of parameters such as precipitation, soil radon concentration, and soil gas permeability were continuously monitored. A theoretical assumption of soil radon concentration was proposed, which was composed of four mechanisms including pore reduce, gas attenuation, cover layer, and rainfall infiltration. A two-layer soil water-air radon transport model was constructed to achieve theoretical simulation of the radon concentration field during rainfall infiltration. The research results show that the four-coupled mechanism model constructed by the two-layer soil model can reproduce the response trend of soil radon concentration in the rainfall experiment, which first rises and then drops. About 94% of the model prediction values fall within the ±2σ range of the measured values, close to the theoretical coverage rate of 2σ confidence level (95.4%). Normalization analysis indicates that the cover layer effect is the parameter among the four mechanisms that is most sensitive to water content changes. The infiltration convective velocity decreases after reaching the peak, revealing the convective upper limit effect caused by the disappearance of the gas phase channel under high water content. As the total rainfall increased from 64 mm to 227 mm, the simulation deviation changed from the lag of radon concentration rise to systematic underestimation. The average absolute error (MAE) increased from 1.96 to 3.81 kBq/m³, reflecting that the model's expression of the surface closure and radon accumulation mechanism caused by the cover layer effect during the heavy rainfall period is not yet sufficient, and there is still needed to improve in the amplitude of the transient response of the four-coupled mechanisms. The research results can provide a theoretical basis for eliminating the interference of rainfall and improving the application of soil radon concentration in radon geological potential mapping and radon data processing in uranium geological exploration.

Key words: soil radon, rainfall, water content, two-layer soil model

中图分类号:

X591

肖磊, 王南萍. 降雨对土壤氡浓度影响的理论模拟与实验研究[J]. 辐射防护, 2026, 46(5): 405-416.

XIAO Lei, WANG Nanping. Theoretical simulation and experimental study on the effect of rainfall on soil radon concentration[J]. RADIATION PROTECTION, 2026, 46(5): 405-416.

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