Radon concentration in soil gas around local disjunctive tectonic zones in the Krakow area

The purpose of this study was to investigate radon in the vicinity of geologic fault zones within the Krakow region of Poland, and to determine the influence of such formations on enhanced radon concentrations in soil. Radon (222Rn and 220Rn) concentration measurements in soil gas (using ionization chamber AlphaGUARD PQ2000 PRO and diffusion chambers with CR-39 detectors), as well as radioactive natural isotopes of radium, thorium and potassium in soil samples (using gamma ray spectrometry with NaI(Tl) and HPGe detectors), were performed. Site selection was based on a geological map of Krakow. Geophysical methods (ground penetrating radar and shallow acoustic seismic) were applied to recognize the geological structure of the area and to locate the predicted courses of faults. Elevated levels of radon and thoron in soil gas were found in the study area when compared with those observed in an earlier survey covering Krakow agglomeration. For 222Rn, the arithmetic mean of registered concentration values was 39 kBq/m3 (median: 35.5 kBq/m3). For 220Rn, the arithmetic mean was 10.8 kBq/m3 and median 11.8 kBq/m3.