COMPARATIVE ANALYSIS ON SOIL RADON EXHALATION RATES AND WEATHER PARAMETERS IN THE ILLINOIS/IOWA QUAD CITIES REGION

Radon (²²²Rn), a naturally occurring radioactive gas in the ²³⁸U decay chain, is the second leading cause of lung cancer in the United States. The Quad Cities are designated by the EPA as a high-risk area for radon exposure due to its geological and soil conditions. The radon found in homes originates primarily from the exhalation of soil gas into the surface gas layer. Measurement of soil radon exhalation may provide key insights into the contributing factors to the variation of radon levels in residences and provide residents a better understanding of exposure risks.

In this study, radon exhalation measurements were collected using two sizes of overturned plastic bins on yard soil (two with ~1 ft³ volumes, and one with ~2 ft³ volume). Each bin contained two RadonEye and one EcoQube detectors, to measure radon exhalation over the course of two months. RadonEye detectors were also placed into three residences surrounding the yard with the bins to allow comparison of indoor radon measurements. To further corroborate the two types of Ecosense detector values, an Airthings CorentiumPro detector was employed in one of the residences and one of the bins for varying durations of time. These results were then compared to weather factors of air temperature, precipitation, humidity, and air pressure.

The results demonstrate cyclical radon exhalation values, ranging from 0.2 to 78.5 pCi/L. Surprisingly high values were registered in all bin detectors, which may be explained by the high surface area to air volume ratios of bins, relative to typical collection areas in basements. An additional consideration of large variation in the radon values may be related to the exhalation occurring in non-diurnal cycles. Preliminary results from correlation analyses on weather conditions showed that air temperature, humidity, and air pressure exhibited the highest correlation to the exhalation values, while precipitation showed minimal effect.

Analysis of soil exhalation rates may provide key insights into the movement of radon into residences. The results from this soil study add to the growing body of radon basement data collected in the Quad Cities region, create a more comprehensive understanding of residential radon measurements, and may help to further inform Quad Cities residents of potential radon exposure risk.