Spatial relationships between radon and topographical, geological, and geochemical factors and their relevance in all of South Korea

The aim of this study was to analyze relationships between radon (Rn) in groundwater and related topographical, geological, and geochemical factors using probabilistic methods in a geographic information system (GIS) environment. A variety of geological and geochemical spatial data were compiled and evaluated for all of South Korea. A spatial database containing information on Rn/U, geology, and geochemistry was constructed for the study area using a GIS. Factors related to the 3,827 Rn occurrences in groundwater were compared with topographical variables such as elevation and slope, geological factors such as lithology, and geochemical measurements such as electric conductivity (EC), oxidation–reduction potential (Eh) carbonate (HCO₃), silica (SiO₂), sodium (Na), potassium (K), magnesium (Mg), strontium (Sr), sulfate (SO₄), nitrate (NO₃), and fluoride (F). Through the use of this spatial database, relationships between areas of Rn exposure and 14 related factors were identified and quantified using probabilistic and statistical modeling (frequency ratios and logistic regression). The results showed that levels of Rn were correlated with topography and main hydrogeological components, specifically elevation, slope, geology, EC, Eh, HCO₃, SiO₂, Na, K, Mg, Sr, SO₄, NO₃, and F, consistent with the results of water–rock interactions in granitic rock formations. The relationship between Rn and U provides clear indication of a geogenic source of radionuclides in the groundwater of granitic rocks in South Korea. These results can be used to map Rn hazards, and the map can be used to provide basic information for environmental management.