Groundwater Radon Risk Mapping in Athens Region, Georgia
Dillon, Marc E.
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Groundwater radon contamination is a common occurrence in areas underlain by granite and by granite gneiss and other high grade metamorphic rocks. In a recent study by Dillon (1989), approximately 300 wells in the Athens region of Northeast Georgia were sampled and the groundwater tested for radon gas. The above area covers almost 9,000 square kilometers located to the east and southeast of Atlanta, Georgia. The area is situated in the Inner Piedmont belt and is underlain entirely by igneous and metamorphic rocks. The available measurements exhibit complex spatial variations which preclude error-free deterministic regional estimation and mapping of groundwater radon contamination. In view of this high degree of variation, a non-linear geostatistical tool, known as indicator kriging is employed to produce spatial risk maps of radon concentrations. The spatial extent of these high risk areas depend on three factors: (i) observed values; (ii) the desired risk level; and (iii) the pre-determined threshold (safe) value of contamination. Such maps will aid a geohydrologist to determine the areas with high risk of radon contamination and target them for more intensive monitoring, remedial, and/or regulatory actions. All computer works and mapping are conducted using GEO-EAS, which is a public domain microcomputer geostatistical environmental assessment software, developed by U.S. Environmental Protection Agency.