Integrated Interpretation of Magnetic and ERT Data to Characterize a Landfill in the North-West of Cologne, Germany

Abstract

Electrical resistivity tomography (ERT) and ground magnetic surveys were applied to characterize an old uncontrolled landfill in a former exploited sand and gravel quarry in an area to the north-west of the city of Cologne, Germany. The total magnetic field and its vertical gradient were recorded using a proton precession magnetometer to cover an area of about 43,250 m2. The magnetic data were transferred to the frequency domain and then reduced to the north magnetic pole. The amplitude of the analytical signal was calculated to define the magnetic materials within and outside the landfill. Eight ERT profiles were constructed based on the results of the magnetic survey using different electrode arrays (Wenner, dipole–dipole, and Schlumberger). In order to increase both data coverage and sensitivity and to decrease uncertainty, a non-conventional mixed array was used. The subsurface resistivity distributions were imaged using the robust (L1-norm) inversion method. The resultant inverted subsurface true resistivity data were presented in the form of 2D cross sections and 3D fence diagram. These non-invasive geophysical tools helped us to portray the covering soil, the spatial limits of the landfill, and the depth of the waste body. We also successfully detected low resistivity zones at deeper depths than expected, which probably be associated with migration pathways of the leachate plumes. The findings of the present study provide valuable information for decision makers with regards to environmental monitoring and assessment.

Visualizing Subsoil Structure for Evaluating the Efficiency of Mole Drain in Heavy Clay Soils Using Geo-electrical Methods

“…Figures (6) compares between the two ERT models produced by the different inversion algorithms. Commonly, the (L1-norm) method is preferred when there are high contrasts in apparent resistivity readings (Ibraheem et al, 2021) because it is less sensitive to bad data points compared to the (L2-norm) method (Dahlin and Zhou, 2004). Since the smoothness-constrain (L2norm) method relies on minimizing the square of the differences between the measured and calculated apparent resistivity, its results were able to show smooth distributions of the inverted resistivity values of the subsoil (Fig.…”

Characterization of a Buried Quarry by Historical Analysis of Satellite Images Integrated with Electrical Resistivity Tomography, East Cairo area, Egypt

“…The ERT data were measured at the investigated site along 16 pro les (P1 to P16) as shown in Figure (4) to locate the land ll zone and determine its lateral/vertical extensions, where the arrows indicate the end of the ERT pro les. For pro les P1-P10 and P15-P16, the Syscal Pro switch instrument was used with 24 electrodes spaced at 5 m to cover a surface distance of 115 m and to attain an investigated depth of about 24 m below the ground surface.…”

Archaeogeophysical exploration in Neuss‐Norf, Germany using electrical resistivity tomography and magnetic data

“…This results in an enhanced 2D resistivity image of the subsurface that is superior to the image obtained by individual array inversion; sensitivity is increased, and uncertainty is reduced by combining the vertical resolution of the Wenner array and the horizontal resolution of the dipole-dipole array (Zhou et al, 2002). This leads to more realistic imaging and interpretation of the revealed anomalies (Ibraheem et al, 2021).…”