Time-variation of the soil gas radon concentration under and near a Swedish house

Although there have been several studies concerning the time variation of radon gas indoors, there have been few studies of the time variation of radon in the soil gas in the earth under or near an occupied house. Since the spring of 1993, the soil gas radon concentration was measured as a time series, at a depth of 1 m in three locations under and near a research house near Stockholm, along with indoor radon and environmental parameters. This report discusses the degree to which the house versus the weather interacts with and influences the soil gas radon concentration, and how much the influence of these two factors on the soil gas radon content varies with season and location. Strong correlations with barometric pressure and outdoor temperature occurred. The maximum soil gas concentrations occurred during the summer months and the minimum occurred during the winter, with the summer and winter levels differing by a factor of 2 to 3, depending on location. Changes in the 24-h averaged indoor radon concentration correlated well with the changes in the soil radon. The degree to which soil gas radon content may be used as an indicator of indoor radon contamination is discussed.