Tectonic control on enhanced geogenic radon as a first order factor in radon hazard assessment

The main goal proposed in this thesis aimed to investigate the tectonic control on enhancing the geogenic radon component as a fundamental factor in radon hazard, and further radon risk, assessment. In particular, the importance of the geogenic radon potential, originated by degassing processes in faulted areas, has been deeply investigated. This so-called Tectonically Enhanced Radon quantity can increase radon availability at surface and its ability to influx within buildings. Mapping the geogenic radon potential represent a crucial tool for both Rn hazard and Rn risk assessment and the first step to identify the Radon Priority Areas as required by the European regulation. To address this goal, the thesis has been developed following two different parallel approaches: at macro- and micro scale. At the macro-scale the potential radon and other soil gases degassing processes along an aseismic fault system and its role on the degassing process as an additional component for the Geogenic Radon Potential has been investigated. Furthermore, a transition from the Rn hazard toward the more comprehensive Rn risk concept has been proposed, in order to suggest a new and clear methodology to define the Radon Priority Areas as required by the European regulation and by the radiation protection objectives. At the micro-scale the potential relationship between Rn migration dynamics and rock deformation mechanisms, has been investigated on three different lithologies, by simulating the seismic cycle using SHIVA apparatus in laboratory. The chosen test area (~60 km2) is located in the Pusteria Valley (Eastern Alps, Bolzano) due to its well-known geological, structural and geochemical characteristics, and the availability of numerous additional data. These evidences increase the knowledge about radon migration mechanisms in different geodynamic environments and will have important implications on the collective risk assessment and the further identification of Radon Priority Areas under a new, more comprehensive geological perspective.