Time-lapse Electrical Resistivity Anomalies due to Contaminant Transport Around Landfills: Forward Modeling Results

This paper presents theoretical geo-electrical responses associated with polluted groundwater flow in porous media around landfills. Forward computation has proven an important role in all stages of geo-electrical surveys. Previous forward studies have emphasized the space-dependence of electrical conductivity, but largely, they ignored its transient feature resulting from the spreading-out of contaminant plumes in directions transverse to the flow path as well as in the longitudinal flow direction. In this research, we adopt a novel `combined' hydrogeological and geo-electrical modeling approach as follows: first using the finite element computer package FEFLOW to simulate contaminant transport and groundwater flow; then establishing the geo-electrical structure based on an empirical relationships between contaminant concentration and water conductivity as well as Archie's law; and finally undertaking the forward computation of geo-electrical anomalies using the finite difference computer packages DCIP2D/DCIP3D. Numerical case studies are conducted for a variety of landfills with different hydrogeological and geological conditions, from which optimal mapping and monitoring configurations are determined.