Radon transport in permeable geological environments.

This article presents the results of a long-term soil radon and meteorological parameter monitoring study in the fault zone at Mt. Beshtau, North Caucasus, which for more than 3 years. Strong seasonal variations in the radon levels with maxima during summer and minima during winter were recorded. The values of radon exhalation and soil radon concentration have a range of 0.025-25 Bq m 2 s -1 and 1-170 kBq m -3, respectively. In addition, measurements of the air radon concentration, and direction of air movement at the adits mouths of the former uranium mine on the same mountain were carried out. Seasonal radon variations, similar to those observed in fault zones, were recorded at the mouths of adits. It was established that radon anomalies are associated with the periodic release of mine air from the fractures and tunnels into the atmosphere. Above an altitude of 900 m a. s. l., an abnormal release of radon occurs in winter, when the mine air is warmer than the surrounding atmosphere. At the altitudes below 900 m the cold radon rich air blows from the adit mouths in summer. During mine air discharge, radon concentrations in the open atmosphere locally around the adit mouth reach 600,000 Bq m-3, averaging 50,000-250,000 Bq m-3. The temporal pattern of radon fluctuations in fault zones and at the adit mouths is similar. A very close correlation between radon levels and atmospheric air temperature was observed both in the fault zone and at the adits mouths. It indicates that radon release in both cases are caused by a single mechanism. This mechanism probably is the atmospheric air circulation in shallow permeable zones due to the temperature difference between the inside mountain and ambient atmosphere.

Factors influencing radon transport in the soils of Moscow.

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 in 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 correlates the most with ambient air temperature both for diffusive and convective radon transport mechanisms, while a weaker inverse correlation is observed with atmospheric precipitation and wind speed for the diffusive mode of radon transport, but not for the convective. Radon activity concentration in soil air correlates with the radon flux density and air temperature in the case of convective radon transport, but does not correlate in the case of diffusive transport.

VARIATIONS IN SOIL RADON LEVELS DURING WINTER AND SPRING PERIODS.

Radon poses significant health risk due to inhalation and subsequent α-decay of its progeny and is the second biggest cause of lung cancer worldwide. In Russian Federation, radon flux density (RFD) measurements are performed routinely to assess radon safety of land lots before construction takes place. This study aims to show possible 'weather'-influenced variations in RFD and radon activity concentration (RAC) that can occur during winter and spring periods in climatic conditions typical for territories with severe snowy winters. Results show that RFD correlates with weather, having a significant correlation with ambient air temperature in winter as well as spring periods and a weak inverse correlation with wind speed. In spring, RFD also responds to an increase in soil moisture, dropping severely because of rainfall. RAC, however, correlates very little with weather but has a weak inverse correlation with RFD.