Solute transport in flow fields influenced by decimetre-scale preferential flow paths: Implications for groundwater remediation

While researchers have devoted considerable effort to examining solute transport influenced by aquifer heterogeneities at either larger scales (metre and above) or at the pore scale, there is a relative paucity of work aimed at the controls administered by decimetre-scale heterogeneity. Recent studies at the Macrodispersion Experiment (MADE) site in Columbus, Mississippi (USA) have indicated that the relative preferential flow paths and flow barriers resulting from dm-scale aquifer heterogeneities appear to have a dominant effect on plume-scale solute transport. These studies suggest that only approximately 15% of the aquifer pore space is involved in advective transport while the remaining 85% serves as a reservoir for essentially immobile solute. The possibility that dm-scale preferential flow paths play such an important role in solute transport has far-reaching implications for groundwater remediation. This paper presents the results of a numerical experiment designed to quantify the key characteristics of solute transport influenced by dm-scale relative preferential flow paths, and discusses the implications for groundwater remediation at a field site.