Infiltration and Redistribution of Perchloroethylene in Stratified Water‐Saturated Porous Media

Abstract

AbstractAlthough infiltration, redistribution, and drainage of dense nonaqueous‐phase liquids (DNAPLs) in water‐saturated soils and aquifers are known to be sensitive to stratifications of the solid phases of the porous media, little experimental evidence is available to explain the behavior of DNAPL movement. To improve our understanding of DNAPL movement under these conditions, physical simulations were conducted with various perchloroethylene (PCE) spills in initially water‐saturated, stratified porous media in nominally one‐dimensional glass columns and in an intermediate scale, nominally two‐dimensional laboratory flow container. The columns and flow container were packed with two distinct layers of coarse sand, with a fine sand layer in between. Volumetric water and DNAPL contents, as well as bulk densities, were determined with a dual‐energy gamma radiation system. To obtain additional information required for the explanation of the displacement processes, in‐ and outflow rates of water and PCE were measured during each experiment. In the sand columns, PCE accumulated on top of the fine layer, while in the flow container, considerable lateral movement was observed just above the fine sand layer. In general, these phenomena were attributed to the small conductivity values of the fine layers relative to those of the coarse layers rather than to displacement pressures not being exceeded. Overall our results suggest that in field situations, continuous PCE spills are more likely to penetrate horizontal fine layers than short intermittent spills.