HIGH INDOOR RADON VARIATIONS AND THE THERMAL-BEHAVIOR OF ESKERS

Measurements of indoor radon concentrations in houses built on the Pis pala esker in the city of Tampere were taken. The objective was to fin d connections between indoor radon concentrations, esker topography, a nd meteorological factors. The results show that not only the permeabl e soil but also subterranean air-flows in the esker strongly affect th e indoor radon concentrations. The difference in temperature between t he soil air inside the esker and the outdoor air compels the subterran ean air to stream between the upper and lower esker areas. In winter, the radon concentrations are amplified in the upper esker areas where air flows out from the esker. In summer, concentrations are amplified in certain slope zones. In addition, wind direction affects the soil a ir and indoor radon concentrations when hitting the slopes at right an gles. Winter-summer concentration ratios are typically in the range of 3-20 in areas with amplified winter concentration, and 0.1-0.5 in are as with amplified summer concentrations. A combination of winter and s ummer measurements provides the best basis for making mitigation decis ions. On eskers special attention must be paid to building technology because of radon.