- 期刊
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Imaging and Detecting Underground Contaminants in Landfill Sites Using Electrical Impedance Tomography (EIT): A Case Study of Lagos, Southwestern, Nigeria
並列摘要
This paper presents an imaging technique called Electrical Impedance Tomography (EIT) which is a purely medical imaging technique, for imaging and detecting underground contaminants in landfill sites in Abule Egba and Solous 1 dumpsites in Lagos, Nigeria. Conventional electrical imaging technique using Wenner configurations was also carried out on each of the sites in order to validate the EIT results. Three methods of impedance data acquisition techniques were employed; neighboring, opposite and cross and the inversion of the data was accomplished using the Electrical Impedance and Diffuse Optical Reconstruction Software (EIDORS) version 3.0 toolkit for MATLAB to obtain three- dimensional conductivity profiles. The scheme utilized in this work is a forward solution solved with a mesh of 768 finite elements with 205 nodes. The conventional electrical resistivity data was inverted using DIPRO software to obtain 2D resistivity structures. With the aid of the 3D impedance tomograms, two distinct contaminant plumes were mapped and identified within and around the landfills. These are highly conductive leachate contaminant plumes with conductivity values ranging from 1,000 to 5,000 mS/m and highly resistive gaseous contaminants (with negative conductivity values on the tomograms) which are probably due to landfill gases as a result of the anaerobic decomposition of the landfill organic wastes. These contaminants are migrating in depths and distance away from the landfills into the aquifer. The study shows that the soil and groundwater system had been contaminated beyond the depth of 50 m in the study areas.