We measured radon (222Rn) concentrations in Iowa and Minnesota and found that unusually high annual average radon concentrations occur outdoors in portions of central North America. In some areas, outdoor concentrations exceed the national average indoor radon concentration. The general spatial patterns of outdoor radon and indoor radon are similar to the spatial distribution of radon progeny i...

Various methods to determine 222Rn concentration in soil gas were tested at two sites with different soil types in a depth of 1 m. They include instantaneous (spot), continuous (real time) and timeaveraging procedures with advective ('active' procedures) or diffusive ('passive' procedures) gas transport from soil to detector: a) active grab-sampling of soil gas from different thin soil gas prob...