Centrifuge Study of DNAPL Transport in Granular Media

The migration potential of dense nonaqueous phase liquids (DNAPLs) in saturated soil was investigated experimentally using the elevated acceleration field of the geotechnical centrifuge. The transport of the DNAPL was monitored with a video camera in flight, through the transparent wall of the sample box. By using measurements of the velocity of the DNAPL front from models corresponding to the same prototype and applying the technique of "modeling of models," the stable infiltration of a low density, high viscosity DNAPL in saturated homogeneous media was shown to scale properly in the centrifuge. The visual observations confirmed the correlations between the DNAPL physicochemical properties and transport patterns, which have important consequences for the characterization of DNAPL-contaminated sites. Infiltrating DNAPLs of high density and low viscosity displace water in an unstable manner and create extensive contaminated areas characterized by non-uniform DNAPL distributions. In contrast, the displacement of water by DNAPLs of low density and high viscosity is stable and efficient, and hence, results in smaller contaminated areas of high DNAPL saturation. Numerical simulations yielded predictions and sensitivity analysis results that agreed well with these experimental observations.