Dielectric Characterization of Soil Samples by Microwave Measurements

Northern high-latitude wetlands are well known to seasonally emit methane gas into the atmosphere, and therefore contribute to greenhouse effects.
While these gas emissions are well documented, their causes are not well understood. The method described in this work can be used to analyze the changes happening in the soil during gas emissions, and therefore help the understanding of the sub-surface gas dynamics.

We have monitored a sample of peat soil through an artificial freezing and thawing cycle, using both a gas detector to measure the methane flux at the soil surface and a vector network analyzer to measure the transmission of microwaves through the soil. It was observed that the results from the two measurement approaches had a very good match under specific microwave signal conditions. In addition, from the microwave measured data, the dielectric properties of the soil and the volumetric fractions of its constituents were also calculated based on a dielectric mixing model.