Radon activity concentrations in the soils of the Gioia Tauro Basin (Calabria, southern Italy), with insights on geo-structural control

The main aim of this work is to map Radon activity concentrations in the soil of a tectonically-active Mediterranean sector (Gioia Tauro Basin, Calabria, southern Italy). A total of 276 measurements have been taken at a depth of ca. 60 cm from the soil surface, using a portable ionisation chamber, according to a pre-established protocol. Measurements have been performed at the centroids of a 2.5 km square grid, and along transverse sections across the main faults. Spatial variation of 222Rn concentrations in soil gas has been modelled through a geostatistical approach, generating 200 realisations by sequential Gaussian simulation. Maps of 222Rn, of 220Rn and of ratio 222Rn / (220Rn + 222Rn) are presented. The distribution of Rn concentrations is highly asymmetrical (median: 14.5 kBq/m3; standard dev. 22.7 kBq/m3; min: 0.06 kBq/m3; max: 137 kBq/m3). The results provide insights into the relationships with the geo-structural characteristics of the territory.