INFLUENCE OF MASS TRANSFER CHARACTERISTICS FOR DNAPL SOURCE DEPLETION IN A HIGHLY CHARACTERIZED FLUVIAL AQUIFER

The transfer of contaminant mass between the nonaqueous and aqueous phases is a process of central importance for the remediation of sites contaminated by dense nonaqueous-phase liquids (DNAPLs). This paper describes a comparison of seven different DNAPL-aqueous-phase mass transfer models for predicting the DNAPL saturation, aqueous-phase plume migration and source depletion time in groundwater systems. The mass transfer models under comparison include those proposed by (1) Miller et al. [1990], (2) Geller and Hunt [1993], (3) Powers et al. [1994a], (4) Imhoff et al. [1994], (5) Powers et al. [1994b], (6) Saba and Illangasekare [2000], (7) Nambi and Powers [2003]. These dissolution models were largely developed through laboratory column experiments. To gain insight into the implications of the various representations of the kinetic mass transfer process at the field scale, the relative performance of each model, taken with the laboratory predicted values of the dissolution parameters associated each, will be analyzed and compared. The hydrogeologic setting is a heterogeneous fluvial aquifer in South West Germany, referred to as the aquifer-analog dataset, that was intensively characterized in three dimensions for hydrogeological parameters that include permeability, effective porosity, grain size, mineralogy and sorption coefficients. By embedding the various dissolution models into the compositional, multiphase flow model, CompFlow, we will explore the relative times predicted for complete depletion of the DNAPL source due to natural dissolution, and if significant environmental benefits can be achieved through DNAPL-zone source removal via enhanced remedial technologies. In this context, the aqueous-phase contaminant concentrations and mass fluxes arriving at a down-gradient compliance boundary will be analyzed in a stochastic framework for the different mass transfer models.