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Measuring Electrical Potentials with LandMapper ERM-02

Electrical geophysical methods are classified as methods measuring natural electrical potentials of the ground without introducing additional electrical field and methods utilizing artificial electrical or electromagnetic fields to measure soil electrical parameters. Method of self-potential (SP) measures the naturally existing electrical potentials in soils and “bio-potentials” in plant, which are important in agriculture. Despite growing popularity of electrical resistivity/conductivity methods in agriculture, method of self-potential is rarely used. The SP method is based on measuring the natural potential differences, which generally exist between any two points in the soil or plant. In addition to measuring ER/EC with four-electrode arrays, LandMapper ERM-02 also allow non-invasively measure natural electrical potentials in soils or between soils and plants, which are very small (µV magnitude) and mostly referred as “noise” potentials in conventional geophysics.

In soil studies researchers are especially interested in the measurement of such “noise” electrical potentials created in soils due to soil-forming process and water/ion movements. The electrical potentials in soils, clays, marls, and other water-saturated and unsaturated sediments can be explained by such phenomena as ionic layers, electro-filtration, pH differences, and electro-osmosis. Soil-forming processes can create electrically variable horizons in soil profiles, thus electrical potential differences measured between soil horizons can be used to study soil forming processes and soil genesis.

Another possible environmental and engineering application of self-potential method is to study subsurface water movement. Measurements of electro-filtration potentials or streaming potentials have been used to detect water leakage spots on the submerged slopes of earth dams (Corwin, 1990). Method of self-potential in addition to EC mapping and vertical electrical sounding/imaging (VES) can aid in archaeological and civil engineering projects (Pozdnyakova et al., 2001).