An Advanced Spatial Approach Based on Multi-criteria Analysis and Geostatistical Simulation for a Comprehensive Geogenic Radon Hazard Index Mapping

Radon concentration originates mainly from geogenic factors, such as uranium content, permeability based on rock unit and tectonic features, as well as karst properties. In this paper, these layers are integrated through a joint spatial multi-criteria approach based on Analytical Hierarchy Process and Fuzzy Gamma Operator techniques, as well as on the Receiver Operating Characteristic curves in order to compare output maps and classify them to construct a Geogenic Radon Hazard Index for Lecce Province in southeastern Italy. To this end, two main criteria and their sub-criteria are defined as contributing factors: geology (uranium content in bedrock, permeability rate in different lithotypes, and faults) and karst features (dolines, caves, and sinkholes). Furthermore, the spatial multi-criteria results, also confirmed by the indoor radon maps generated through Sequential Gaussian Simulations, show that the sites rich primarily in uranium content in bedrock, faults, and sinkholes can be identified as the most critical areas. Finally, the evaluation of the performance is completed through the Success Rate Curve, which demonstrates the efficiency of the Fuzzy Gamma Operator method and corroborates that this innovative spatial multi-criteria approach can support the production of reliable maps of high radon potential areas. This approach encourages the development of effective risk reduction strategies for future planning and targeted sampling in areas with limited indoor radon data.