Factors Influencing Radon Transport in the Soils of Moscow

Abstract This article delves into the factors that may influence radon flux, such as soil properties and weather conditions on the example of two experimental locations with different soil compositions, composed primarily of clay and sand respectively. The experimental location with sandy soil was previously observed to have anomalously high radon flux levels. Radon monitoring was performed routinely, approximately at the same time of day and in parallel on both of these locations to exclude the influence of diurnal variations. The results show that radon transport on these locations differs in mechanism: location with clay soil has diffusive radon transport, with an average radon flux density of 37.4 ± 24.9 mBq m-2 s-1 and a range of 0.3 – 167.8 mBq m-2 s-1, while the location with sandy soil has convective radon transport with an average radon flux density of 93.6 ± 51.2 mBq m-2 s-1 and a range of 9.8 – 302.2 mBq m-2 s-1. This corresponds to about 8.3% of RFD measurements on site with clay soils exceeding the national reference level of 80 mBq m-2 s-1 and 45.6% exceeding them on the site with sandy soils. Average radon flux density values were then compared to meteorological variables using Pearson correlation analysis with Student’s t-test. It was observed that radon flux density inversely correlates most strongly with ambient air temperature in both cases, while a weaker inverse correlation is observed with atmospheric precipitation and wind speed for the diffusive radon transport. Radon activity concentration in soil air correlates with the flux density and air temperature only in the case of convective radon transport and does not correlate with anything else.