Modeling of Density-Dependent Flow and Transport in Anisotropic Aquifers: An Example Site of Landfill

Abstract

In advection-dispersion transport processes, the density contrast between the contaminant fluid and the groundwater in the surrounding flow domain can affect the groundwater flow. Under such circumstances, the migration patterns and concentration distributions of contaminant plumes can be changed. The primary purpose of this research is to simulate the problems of density-dependent groundwater flow and transport in homogenous, anisotropic and inhomogenous (or heterogenous), anisotropic aquifers by means of a Galerkin finite element method. Secondly, this research is to show the numerial model of Galeati et al. (1992) can be applied to a landfill site.
The leachate from a landfill site into the groundwater can change theconta1ninant concentration. Thus, there exists a density contrast between the contaminant fluid and the groundwater in the surrounding flow domain. In simulation, an example site of landfill is demonstrated. The results for conta1ninant sources from a landfill conclude as follows. If there d s not exist a significant density contrast, the contaminant plume will spread in a shallow zone close to the water table; on the other hand, if there is such a contrast, the plume will sink downward into the groundwater flow system, and its migration pattern will only be changed after a longer transport time of six years. In a shorter time (one to three years), however, the migration pattern will not be significantly changed.

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