Groundwater pollution by organic compounds: A two-dimensional analysis of contaminant transport in stratified porous media with multiple sources of non-equilibrium partitioning

Transport of pollutants in soil and groundwater often occurs in stratified media under non-equilibrium conditions. Confined aquifers are usually bound ed by low-permeability layers of soil which have been shown to exert a sign ificant influence on the fate of contaminants in groundwater. Numerical sol utions of transport equations have usually been restricted to single layers and have included single sources of non-equilibrium processes or none at a ll. The effect of soil stratification itself has sometimes been reduced to a transport-based non-equilibrium process. A boundary element solution of the transport equations in the Laplace domai n is extended to include multiple sources of non-equilibrium processes in s aturated media under the assumption of rate-limited mass transfer. Green fu nctions accurately model infinite and semi-infinite domains such as soils a nd Laplace transforms remove the need for time-stepping and the associated numerical complexity. The proposed numerical technique is validated by comp aring its results to analytical solutions. Its scope is illustrated through a case study of a sand aquifer bounded by less permeable layers of silt, a nd infiltrated by pollutants from a neighbouring lake. Copyright (C) 1999 J ohn Wiley & Sons, Ltd.