Climate impact on radon risk for silty loam soils

Radon isotope ²²²Rn constitutes a natural source of radioactivity, which is worldwide extended and can be found, regardless its concentration in almost all soils of the Earth surface. Inhale radon gas is a risk for human health and the World Health Organization, WHO, has concluded the doubtless correlation between long exposure to radon gas and lung cancer; even more, the US-EPA considers it as the second most important cause of lung cancer in USA., The adoption of preventive measurements during building construction is extending in many developed countries because long exposure to radon gas take place mainly in poorly ventilated basements. Generally, these measures are based on radon risk associated exclusively with radon production by soils, but less attention are devoted to the impact of soil gas permeability and, even more, of the variable soil gas permeability because of the different degrees of soil water contents. Soil water content affects soil permeability to both water and vapor phases, and it must be taken into consideration when defining the risk associated to the presence of radon. In the present study, we show the importance of different climate conditions on soil water content and in turn on the gas permeability. We tested with the radon potential risk of building sites of the Czech Republic, which combines both the radon concentration in soil and soil gas permeability (Neznal et al, 2004). According to the Köppen classification, the present study considers different climatic scenarios: Bsk, hot semiarid climate, typical from many regions in South Europe; Csa, temperate Mediterranean climate with dry hot summers and moderate winters, also common in South Europe; Cfb, oceanic humid climate with great extension in France and UK; and finally Dfb, humid continental climate with cool winters and moderate summers, typical from central Europe.

Soil water content for each scenario was simulated using HYDRUS. Average values were obtained from a 100-year temporal series.  The top most 1-m thick layer was considered as the representative for the soil water content. Results demonstrate the necessity to consider water content when defining the radon risk and their interannual variability, especially for those climates with very clear different precipitation patterns along the different seasons.