Spatial variation of waterborne radon and temporal variation of radon in water at nine Maine schools.

Nine elementary schools in Maine were examined to track the release of 222Rn and to determine the transfer coefficient from water into air. Water-use simulations were performed by running sinks and sprayers for 1 h in a kitchen. The 222Rn in air was measured over 24 h throughout the school. The subsequent release of 222Rn into the kitchen air was measured to be greater than the EPA action level of 0.15 Bq L-1 (4 pCi L-1), but negligible concentrations of 222Rn were found in adjacent classrooms. In two schools, more than 10 222Rn-in-air detectors were placed throughout the kitchen and showed a three-fold spatial concentration variation. During the hour-long simulations, the 222Rn in water concentration was measured periodically, and many of the schools showed an increase in the 222Rn concentration in water before remaining constant. These measured variations suggest that multiple detectors are needed to accurately measure waterborne 222Rn in air, and multiple delayed measurements of 222Rn dissolved in water are needed to obtain a representative groundwater sample.