A pilot study of the dependence of radon concentration on the tectonic structures, using simple geophysical methods.

It is well known that there are great variations in radon concentrations in the soil gas on building sites. The concentration may sometimes vary by more than two orders of magnitude. The tectonic structure of the bedrock is one of the factors that influence the intensity of the radon outflow. The simple ARES geophysical method [automatic resistivity system--main unit with standard accessories, multi-electrode cable sections (MCS5)--eight electrodes per 5 m spacing] was used in various modes (Schlumberger, Dipole-Dipole and Pole-Dipole arrays) for in situ tectonic structure determination. The radon concentration in the soil gas was measured using the same network as for the resistivity measurements. The radon measurements were also followed up by in situ gamma spectrometry measurements. The behaviour of the radon concentration in the soil gas was correlated with the detected tectonic non-homogeneities. This pilot study opened up new questions for future analysis.