Radon concentration in soil gas and radon exhalation rate at the Ravne Fault in NW Slovenia

Abstract

The Ravne tectonic fault in north-west (NW) Slovenia is one of the faults in this region, responsible for the elevated seismic activity at the Italian-Slovene border. Five measurement profiles were fixed in the vicinity of the Ravne fault, four of them were perpendicular and one parallel to the fault. At 18 points along these profiles the following measurements have been carried out: radon activity concentration in soil gas, radon exhalation rate from ground, soil permeability and gamma dose rate. The radon measurements were carried out using the AlphaGuard equipment, and GammaTracer was applied for gamma dose rate measurements. The ranges of the obtained results are as follows: 0.9–32.9 kBq m^&minus;3 for radon concentration (<i>C</i>_Rn), 1.1–41.9 mBq m^&minus;2 s^&minus;1 for radon exhalation rate (<i>E</i>_Rn), 0.5–7.4&times;10^-13 m² for soil permeability, and 86–138 nSv h^&minus;1 for gamma dose rate. The concentrations of ²²²Rn in soil gas were found to be lower than the average for Slovenia. Because the deformation zones differ not only in the direction perpendicular to the fault but also along it, the behaviour of either <i>C</i>_Rn or <i>E</i>_Rn at different profiles differ markedly. The study is planned to be continued with measurements being carried out at a number of additional points.