Dissolution and contaminant transport in aquifers with spatially and temporally variable hydraulic properties

In evaluating the potential of entrapped nonaqueous phase liquid (NAPLs) sources to contaminate groundwater or in designing remediation, it is necessary to know the rates at which NAPL dissolves into water. These mass transfer rates significantly influence the downstream contaminant concentration and also the spatial extent of contamination. Understanding the dynamics of the mass transfer process under two-dimensional (2D) flow fields and developing a generalized contaminant transport model is the primary focus of this paper. The NAPL dissolution experiments were conducted in a 2D porous media system for four different initial NAPL saturations (Sn = 0.19; Sn = 0.56; Sn = 0.76; Sn = 0.93) covering extremities from very low to very high NAPL saturations. All the model parameters used in the transport model are either determined experimentally or estimated from empirical relations except for the mass transfer coefficient and relative permeability of the aqueous phase. A total of nine simulations were run with various combinations of mass transfer and relative permeability correlation. The contaminant transport model developed in the present study was sensitive to inaccurate measurements in effective permeability and intrinsic permeability, whereas it is relatively insensitive to variation in dispersivity values within ±1 degree magnitude. © 2012 by Begell House, Inc.