Geometrical factors and interfacial processes affecting complex dielectric permittivity of partially saturated porous media

Methods for remote and ground-based sensing of soil water content often rely on determination of bulk dielectric permittivity which may be affected by factors other than water content, such as interfacial polarization (Maxwell-Wagner effect), phase configuration, and electrical conductivity. The complex interactions among these factors were modeled by the Maxwell-Wagner-Bruggeman-Hanai formalism on the basis of self-consistent differential effective medium approximation. The modeling framework considers porous media composed of coated inclusions and enables systematic evaluation of various factors on determination of water content at different measurement frequencies associated with different sensors. Simulation results illustrate the importance of accounting for phase configuration; using a simple saturation-dependent weight function and only two typical phase configurations provided good agreement with a wide range of dielectric measurements spanning different porous media, saturations, and measurement frequencies. The model provides the necessary framework for incorporation of the Maxwell-Wagner effect on standard measurements obtained by time domain reflectometry and through frequency response enables evaluation and a wide array of other sensors. Work is under way to incorporate effects of ambient conditions (temperature) and of bound water on bulk dielectric measurements.