The Empirical Bayesian Regression Kriging (EBRK) to map the Geogenic Radon Potential (GRP). A case of study from the Euganean Hills (Italy)

In the volcanic area of the Euganean Hills district (100 km2), the indoor radon often exceeds the threshold level of 300 Bq/m3 stipulated by the Council Directive 2013/59/Euratom, thus suggesting the need to investigate the possible link between observed radon concentrations and the local geology (Trotti et al., 1998,1999; Strati et al., 2014). More recently, statistical and geostatistical analysis on rock samples identified high U, Th and K concentrations associated with areas characterised by trachyte and rhyolite lithologies (Tositti et al., 2017). With this contribution, we completed our investigation on the natural radioactivity in the Euganean Hills district extending the rocks dataset, performing on-site soil gas survey, and considering other important factors which can locally increase the radon occurrence, such as hydrothermal alterations, types of soils (e.g., geochemistry or presence of organic matters), and faults. Furthermore, we elaborated a Geogenic Radon Potential map to assess the local spatial relationships between the measured soil gas radon concentrations and seven proxy-variables: fault density (FD), total gamma radiation dose (TGDR), 220Rn (Tn), digital terrain mode (SLOPE), moisture index (MI), heat load index (HLI) and soil permeability (PERM). Empirical Bayesian Regression Kriging (EBRK) was used to develop the most accurate hazard map of the considered area, thus, providing the local administration an up- to-date decisional tool for the land use planning. For the high radon emission measured, the high density of dwelling, and its geomorphological features, the Euganean Hills district represented a very meaningful case of study.