Groundwater Research, Rosbjerg et al (eds) 2000 Balkema, Rotterdam, ISBN 90 5809 133 3

Radon-222 as an indicator of subsurface NAPL contamination

M. Schubert, K, Freyer, H.C. Treutier & H. Weiss
UFZ Centre for Environmental Research Leipzig Halle GmbH, Leipzig, Germany

Keywords: radon, NAPL contarnination, soil, detection method

ABSTRACT: Underground NAPL contamination is one of the major problems in the remediation of polluted industrial sites. Contamination likely to affect groundwater quality is of particular concern. Due to the mostly limited number of monitoring and sampling points it is often difficult to track the extent of subsurface NAPL contamination. To permit a more detailed assessment of NAPL plumes, a new detection method has been developed. The method uses local minima of the soil gas radon (²²² Rn) concentration to indirectly locate NAPL contamination. Since 222 Rn is a naturally occurring and easily detectable component of the soil gas, the method allows a dense network of monitoring points. The use of 222 Rn as an indicator of NAPL contamination is possible due to the good solubility of 222 Rn in NAPLS, enabling them to act as a 'radon trap'.