Modeling of geogenic radon in Switzerland based on ordered logistic regression

AbstractPurposeThe estimation of the radon hazard of a future construction site should ideally be based on the geogenic radon potential (GRP), since this estimate is free of anthropogenic influences and building characteristics. The goal of this study was to evaluate terrestrial gamma dose rate (TGD), geology, fault lines and topsoil permeability as predictors for the creation of a GRP map based on logistic regression.MethodSoil gas radon measurements (SRC) are more suited for the estimation of GRP than indoor radon measurements (IRC) since the former do not depend on ventilation and heating habits or building characteristics. However, SRC have only been measured at a few locations in Switzerland. In former studies a good correlation between spatial aggregates of IRC and SRC has been observed. That’s why we used IRC measurements aggregated on a 10 km × 10 km grid to calibrate an ordered logistic regression model for geogenic radon potential (GRP). As predictors we took into account terrestrial gamma doserate, regrouped geological units, fault line density and the permeability of the soil.ResultsThe classification success rate of the model results to 56% in case of the inclusion of all 4 predictor variables. Our results suggest that terrestrial gamma doserate and regrouped geological units are more suited to model GRP than fault line density and soil permeability.ConclusionOrdered logistic regression is a promising tool for the modeling of GRP maps due to its simplicity and fast computation time. Future studies should account for additional variables to improve the modeling of high radon hazard in the Jura Mountains of Switzerland

MODELLING THE EXPOSURE OF RESIDENTS OF A RADIUM-CONTAMINATED LIVING PLACE

Abstract Within the framework of the Swiss Radium Action Plan 2015–22, which aims to investigate and remediate sites contaminated by the radium used in the Swiss watch industry, a reference level of 1 mSv per y has been defined for the exposure of residents. An additional protection objective has been set for soil contamination, which should not exceed the value of 1000 Bq per kg 226Ra. Based on measurements on the study sites, the doses received by residents were calculated accordingly to the methodology, in both indoor and outdoor areas, taking into account external exposure and ingestion. The site diagnosis approach consists of a screening procedure based on a rapid measurement, followed, if necessary, by additional analysis to estimate doses. Sites where modelling indicates that the reference level or the complementary protection objective for soil contamination have been exceeded are subject to remediation. The application of the methodology based on these radiological criteria to 752 sites diagnosed until December 2020 indicates a rate of sites (buildings and outdoor areas) requiring remediation of ~16%. The annual doses to residents calculated by modelling are between 1 and 20 mSv per y for these sites.</jats:p