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 (222Rn) concentration to indirectly locate NAPL contamination. Since 222Rn is a naturally occurring and easily detectable component of the soil gas, the method allows a dense network of monitoring points. The use of 222Rn as an indicator of NAPL contamination is possible due to the good solubility of 222Rn in NAPLs, enabling them to act as a ‘radon trap’.
