RN-222 IN WATER - A STUDY OF 2 SAMPLE COLLECTION METHODS, EFFECTS OF MAILING SAMPLES, AND TEMPORAL VARIATION OF CONCENTRATIONS IN NORTH-CAROLINA GROUNDWATER

The U.S. Environmental Protection Agency has proposed a drinking water standard for Rn-222 in public water supplies. When promulgated, operators of public water supplies will be required to determine water Rn-222 concentrations. Most likely, water samples will be collected and mailed to laboratories for analyses. Additionally, it is probable that homeowners will test private well water in a similar manner by collecting water samples and mailing them to a laboratory for Rn-222 analyses. In anticipation of these actions, this study was conducted to evaluate two methods of water sample collection and to evaluate the potential losses of Rn-222 from water samples mailed to a laboratory. Thirdly, temporal variations in Rn-222 concentrations in several groundwater supplies in North Carolina were examined. Water supplies at four sites in eastern North Carolina and five sites in western North Carolina were sampled over a 7-mo period beginning in the fall of 1993 and continuing through the spring of 1994. Samples were analyzed using a liquid scintillation method. This study showed that a ''slow-flow'' method is not only suitable for sample collection, but may be the preferable method for water sample collection since slow-flow collection resulted in less Rn-222 loss than was observed during syringe collection, i.e., the water Rn-222 concentrations in samples collected by the slow-flow method were generally higher. Further, based on this study, mailing water samples to a laboratory for analysis should not have a substantial effect on the measured Rn-222 concentrations. Consequently, water samples can be collected by the slow-flow method by water supply operators, as well as homeowners, and mailed to laboratories for Rn-222 analyses with reasonable assurance that the samples have not suffered significant Rn-222 loss. Temporal variations in water Rn-222 concentrations were observed in this study. One factor complicating the study of temporal variations in Rn-222 concentrations was the striking influence that inconstant water usage and inadequate well purging prior to sample collection had on Rn-222 loss from the water.