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 ((222)Rn) 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 for(222)Rn 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 mean(222)Rn concentrations of groundwater associated with different types of rocks. The data, however, also indicate that there is a great degree of variability in the(222)Rn 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 of(222)Rn concentration. The present study indicates that use of these variables as predictors does not significantly improve the likelihood of locating water supplies with elevatec(222)Rn concentrations.