VEGETATED TREATMENT OF VEHICLE WASH SEDIMENTS: MATHEMATICAL MODELING OF GROUNDWATER AND SOLUTE TRANSPORT

In modeling a phytoremediation strategy, the transport and fate processes of soil water are influenced by subsurface groundwater flow, precipitation events, microbial activity, and transpiring vegetation. This transport is modeled in a variably saturated environment in a vertical dimension and is represented by a Richards equation supported with a van Genuchten model as its constitutive relations. The fate and transport of solutes considers various physicochemical phenomena such as adsorption, volatilization, gas-phase diffusion, with biodegradation by soil microbes and plant uptake, as fate processes of the solutes. Volatilization of contaminants is treated as an open-contaminant, evaporative-flux boundary condition at the soil surface. Vegetation may play an important role by enhancing indigenous soil microbial degradation and by absorbing or transpiring the contaminants. The validated model will be employed to investigate the fate and transport processes occurring in an actual hydrocarbon-contaminated field site. The model results will be used as part of a decision support system to predict the soil conditions, plant activities, and contaminant fate processes in the soil environments for the simulation period.