Geoelectrical Techniques For Subsurface Characterization And Contaminant Plume Images At Landfill Sites
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Date
2016-08
Authors
Abdulrahman, Abdullahi
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Abstract
An interpretation template for the analysis of electrical resistivity and chargeability inverse models produced at two upgraded semi-aerobic landfill sites was developed. The inverse models generated from a 2D inversion program (RES2DINV) were used to set up grids of resistivity and chargeability imaging at the landfill sites. The study confirmed a low resistivity (<10 Ωm) depicting leachate plume while a high chargeability unit (>70 ms) represents waste deposits and saturated clayey layers. Furthermore, the IP responses of the disseminated leachate plume downstream of a separate landfill site were assessed. The appraisal also examines the contaminant status and classified the strata beneath municipal solid waste landfills. The outcome of the investigation showed that the ion-dominated plume displays a weak chargeability zone (<20 ms) and supports ionic polarization rather than electronic polarization in its IP responses. However, the high concentration of ions in the diffused leachate inhibits the membrane polarization, thus reducing the IP effects in host sediments. The outline of resistivity and chargeability profiles with average percentage error of about 15% at the characterization sites and assessment site shows differentiated zones of the subsurface strata. Comparison of the leachate columns at the characterization sites revealed that the closed landfill with a higher proportion of waste deposits contained a lesser accumulation of leachate than the active site. 3D resistivity and chargeability inverse
models were generated at the leachate assessment site using the RES3DINV inversion program. The horizontal slices from the 3D inverse models were utilized for the contaminant plume mapping and quantification. Additionally, physiochemical analysis and porosity evaluation conducted at this site enabled a full qualitative and quantitative assessment respectively. Despite the aeration ponding, the physiochemical results confirmed that some of the pollution indices measured at the downstream of the site were not within the Malaysian approved leachate discharge limits. The porosity estimation for the un-sampled soil sections using a basic geostatistical approach provided the platform for leachate quantification at the survey area where a total of about 1.6 x 105 m3 amount of contaminant plume was estimated. In this process, empirical expressions were derived between geophysical and geotechnical quantities portraying the characteristics of downstream of a landfill site. Delineation of the contaminated sites in this study supports the effectiveness of contaminant plume monitoring and could lead to a promising reconnaissance tool for remediation or reclamation of solid waste disposal sites.
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Analysis of electrical resistivity and chargeability inverse models produced , at two upgraded semi-aerobic landfill sites was developed.