Application of Multiphase Dielectric Mixing Models for Understanding the Effective Dielectric Permittivity of Frozen Soils

Abstract

The me domain refl ectometry (TDR)-measured eff ec ve permi vity in frozen soil condi ons is aff ected by many complex factors including bound water eff ects on soil water permi vity, phase changes, soil microstructure and rela ve posi ons of soil cons tuents with respect to each other. The objec ve of this study was to improve understanding of some of the factors aff ec ng the eff ec ve permi vity of frozen soils through the use of dielectric mixing models. Published datasets and frozen and unfrozen soil data measured on western Canadian soils were inves gated with mul phase discrete and confocal ellipsoid models available in the literature. The results revealed that adjus ng model parameters allowed the mixing models to describe the frozen soil permi vity equally well when bound water eff ects and temperature-dependent water permi vity eff ects were included or not included. Measurement of freezing and thawing curves on western Canadian soils showed signifi cant hysteresis and some mechanisms for this observed hysteresis and its infl uence on the interpreta on of published datasets are discussed. When independent measurements of liquid water, ice and eff ec ve permi vity are available, it is possible to fi nd one set of model parameters that reasonably predict eff ec ve permi vity for both frozen and unfrozen condi ons. In frozen soils the predic ve capability of the models is constrained to scenarios where the ini al water content prior to freezing (i.e., the total water content) in the sampling volume is constant.

Local- and Plot-Scale Measurements of Soil Moisture: Time and Spatially Resolved Field Techniques in Plain, Hill and Mountain Sites

“…For these last applications, the adoption of a steel guide during the insertion process is strongly recommended to maintain rods in parallel and prevent geometrical probe deformations. Due to the TDR's inability to detect liquid and ice contents simultaneously (within a bandwidth between a few megahertz and 1.5 GHz), in the case of frozen soils additional measurements with lower frequencies (between 0.1 and 200 kHz [118,119]) would be necessary to avoid underestimations or errors.…”

“…Accordingly, the most intense reaction is observable in the data collected by the shortest probes (in Figure 7 represented by the 0.30 m lengths), which investigate the shallowest layer. Moreover, during the winter months, the presence of frozen topsoil can lead to TDR measurement complications due to the TDR's inability to detect simultaneously liquid and ice contents in frozen soils within the bandwidth included between a few megahertz and 1.5 GHz [118,119]. These complications, if not properly considered, can cause measurement errors proportional to the soil depth reached by the frost in relation to the depth investigated by the probes.…”

Soil freezing–thawing characteristics and snowmelt infiltration in Cryalfs of Alberta, Canada

“…To estimate the unfrozen water content (θ l ) and ice content (θ i ), the discrete dielectric mixing model presented in He and Dyck (2013) was used. The model was modified and calibrated from the discrete ellipsoid model that was initially developed by Sihvola and Lindell (1990).…”

“…(e.g., Bittelli et al, 2004;Watanabe and Wake, 2009;He and Dyck, 2013), has greatly improved the measurement of unfrozen water in frozen soil. The improved unfrozen water measurement then can be used to better reflect the soil freezing characteristics (SFC) or soil freezing-thawing curves (SFTC) in lab and field conditions, respectively.…”

Soil Water and Phreatic Evaporation in Shallow Groundwater during a Freeze–Thaw Period

“…The frozen soils are characterized by the coexistence of liquid water and ice. Many methods have been used for measuring liquid water content, such as time-domain reflecometry (TDR) [42,43] and nuclear magnetic resonance (NMR) [44], as well as ice content, such as dielectric spectroscopy [45] and the heat pulse probe [46], in frozen soil. Some investigators have combined two methods together to infer the total water content in frozen soil; for example, gamma ray and TDR [47], and neutron probe and TDR [48].…”