Non-Invasive 3D Conductivity Measurements With Merit

The non-invasive measurement of physical parameters in soil columns is an important tool for<br>a profound insight into flow and transport processes in soils. We present the Magneto-Electrical Re-<br>sistivity Imaging Technique (MERIT) in theory and application to investigate the three-dimensional<br>distribution of the electrical conductivity in a soil column. This method is based on the combined<br>measurement of both electric potential and magnetic eld distributions resulting from numerous<br>low-frequency (i.e. <100Hz) current injections. Thus, it represents a merger of conventional elec-<br>trical resistance tomography (ERT) with magnetometric resistivity (MMR) measurements. Three-<br>dimensional nite-element modeling of the electric potential and the magnetic eld for a conductive<br>cylinder is performed to investigate the di erences between the model parameter resolution charac-<br>teristics of ERT and MMR measurements. Application of linear inversion theory on synthetic data<br>indicates the superior capability of MERIT. It turns out that the magnetic eld contains additional<br>valuable information on the conductivity distribution of the soil sample, which is expected to lead<br>to an improved spatial resolution when used for tomographic imaging in conjunction with ERT.