Predicting DNAPL mass discharge from pool-dominated source zones.

Models that link simplified descriptions of dense non-aqueous phase liquid (DNAPL) source zone architecture with predictions of mass flux can be effective screening tools for evaluation of source zone management strategies. Recent efforts have focused on the development and implementation of upscaled models to approximate the relationship between mass removal and flux-averaged, down-gradient contaminant concentration (or mass flux) reduction. The efficacy of these methods has been demonstrated for ganglia-dominated source zones. This work extends these methods to source zones dominated by high-saturation DNAPL pools. An existing upscaled mass transfer model was modified to reproduce dissolution behavior in pool-dominated scenarios by employing a two-domain (ganglia and pools) representation of the source zone. The two-domain upscaled model is parameterized using the initial fraction of the source zone that exists as pool regions, the initial fraction of contaminant eluting from these pool regions, and the flux-averaged down-gradient contaminant concentration. Comparisons of model predictions with a series of three-dimensional source zone numerical simulations and data from two-dimensional aquifer cell experiments demonstrate the ability of the model to predict DNAPL dissolution from ganglia- and pool-dominated source zones for all levels of mass recovery. Published by Elsevier B.V.