222Rn concentration changes in medicinal groundwaters of L dek Zdrój (Sudety Mountains, SW Poland)

L dek Zdrój in southwestern Poland is a place where thermal groundwaters, regarded as medicinal, outflow. They contain, amongst other characteristic parameters, enhanced quantities of 222Rn, which is dissolved in these waters in the area of their outflow to the surface. Distinct fluctuations in its concentrations with time (from 35 to 55%) are characterised by irregularity and vary for particular intakes, showing a non-changing trend (D brówka intake), a falling trend (Chrobry, Sk odowska-Curie, L-2 intakes) or a growing trend (Jerzy and Wojciech intakes) in the last several tens of years, although the waters are of the same hydrochemical type and flow out of the same hydrogeological structure. There is no seasonal variation in 222Rn concentrations in these waters except in the Jerzy intake, where a 6-month cycle was observed in the years 1970–1971. However, the fluctuation amplitude was insignificant in comparison to those of the irregular fluctuations. It seems that the changes in 222Rn concentrations in the thermal groundwaters of L dek Zdrój may be caused by atmospheric factors, such as temperature, pressure, humidity and by the discharge of the intakes.