Radonove mereni na Labske a Pancavske louce v Krkonosich

Within the framework of the project "The complex analysis of the long term changes of Krkonoše tundra" the complex geophysical research is being realized in the western Krkonoše area since 2000. In the year 2003 the main part of the exploration consisted in radon measurement in the area of Labská and Pančavská louka. An area of 1500 x 2500 m was explored in the net 300 x 300 m by means of RDA 200 (Scintrex) instrument. The volume-activity (cA) determination of radon 222Rn and 220Rn was conducted on three points at each station, the soil gas was pumped from a depth of 50 cm. The locality lies within the Krkonoše-Jizera granite massif and its bedrock in the northern part is formed by medium- to fine- grained biotite granite and in the southern part by porphyric and medium- grained biotite granite. The geophysical research proved the high volume-activities of radon 222Rn (simple average 260 kBq . m-3) as well as 220Rn (simple average 145 kBq . m-3) throughout the explored area. The extreme activity of 222Rn reaches a value of 902 kBq . m-3. The corresponding, re-counted average concentration of uranium in the granite bedrock is 18 ppm, the topmost one is approximately 60 ppm. Maxima of 222Rn and 220Rn volume-activities are probably linked with contact zones between different-grained granite types. The prominent zone of high activities intersects the locality in NW-SE direction (Fig. 1).