TitleNS16A-01 - In search of low-frequency surface charge relaxation signatures of porous media in low frequency electromagnetic induction data
Session Start2022-12-12 16:45:00 CST
Session End2022-12-12 18:15:00 CST
LocationMcCormick Place, S106a
AuthorDan R
AbstractLow frequency electrical relaxation phenomenon can be observed in porous materials and is related to the ability of grain surfaces to conduct locally bound electrical charge. Bound charges associated with the electrical double layer and ions in solution polarize in the direction of the electric field. Measurements of this relaxation phenomenon can be a useful tool to quantify the specific surface area of a given sample remotely. To date this type of frequency dependent measurement has been limited to galvanic observations at the laboratory and field scales. Transitioning from galvanic to standoff observations through electromagnetic induction sensors. Previously, we have presented investigations where measurements of the secondary magnetic field response from porous media in the frequency range of 100 kHz through 20 MHz were examined for evidence of relaxation signatures using a high-frequency electromagnetic induction sensor (HFEMI). Here, we evaluate a newly constructed low-frequency electromagnetic induction sensor (LFEMI), capable of measurements in the 3 Hz to 1 kHz range. These systems have demonstrated performance for metal detection in the form of ohmic relaxation. In this work, we present results of experiments designed to observe surface relaxation responses in porous materials as a result of bound charge transfer, i.e. surface conductivity rather than Ohmic conductivity. The ability to measure this phenomenon remotely has the potential for broad impact within the subsurface interrogation communities including proximal soil sensing, environmental monitoring, geotechnical assessment, and hydrogeologic investigations.