Predicting the occurrence of radon-222 in groundwater supplies

The intent of this study was to develop an understanding of some of the factors that affect the concentration ol radon-222 (²²²Rn) in drinking water supplies derived from groundwater, with specific application to North Carolina. Data for this investigation were collected on a sample of 96 North Carolina public water supply wells. Water samples were collected and analyzed for²²²Rn content. Data on site geology and well characteristics (discharge, specific capacity, depth, and casing length) were obtained from existing sources. From a statistical examination of the data collected in this study, we conclude that there is a distinct and statistically significant difference in the mean²²²Rn concentrations of groundwater associated with different types of rocks. The data, however, also indicate that there is a great degree of variability in the²²²Rn concentrations of samples drawn from any giver rock type. The situation is made slightly better by introducing a second variable given as the geologic region of a water supply. A fairly surprising finding of this study is the relative insignificance of discharge, specific capacity, depth, and casing length of wells as predictors of²²²Rn concentration. The present study indicates that use of these variables as predictors does not significantly improve the likelihood of locating water supplies with elevatec²²²Rn concentrations.