Temporal variability of radon in the atmosphere of Domica and Važecká Karst caves (Slovakia)

Continual monitoring of radon activity concentration was performed in two caves: Domica and Važecká. Radon in the air of the Domica cave was monitored from June 2010 to July 2011. Radon research in the Važecká cave started in June 2012 and it is still being carried out. Radon concentration in cave atmosphere exhibited seasonal, short-term and daily variations. Daily average of radon in Domica varied from 0.5 to 2.7 kBq m(-3). Seasonal trend was characterised by the highest concentration in September and the lowest from February to March. Radon concentration in the Važecká cave was significantly higher, and the daily average ranged from 1.0 to 5.3 kBq m(-3). The highest values were registered from June to September and in January. The seasonal and daily variations of 222Rn activity concentration in the atmosphere of both caves are assumed to be associated with the atmospheric temperature. No effect of atmospheric pressure on radon short-term variation was found.