Miscellaneous methods for determination of unfrozen water content in frozen soils

Authors: FENG, SHUNA - Northwest A&f University; CHEN, JUNRU - Northwest A&f University; JONES, SCOTT - Utah State University; Flerchinger, Gerald; DYCK, MILES - University Of Alberta; FILIPOVIC, VILIM - University Of Queensland; HU, YOU - Jiangxi Academy Of Agricultural Sciences; SI, BINGCHENG - University Of Saskatchewan; LV, JIALONG - Northwest A&f University; WU, QINGBAI - Chinese Academy Of Sciences; HE, HAILONG - Northwest A&f University

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2023
Publication Date: 1/28/2024
Citation: Feng, S., Chen, J., Jones, S., Flerchinger, G.N., Dyck, M., Filipovic, V., Hu, Y., Si, B., Lv, J., Wu, Q., He, H. 2024. Miscellaneous methods for determination of unfrozen water content in frozen soils. Journal of Hydrology. 631. Article 130802. https://doi.org/10.1016/j.jhydrol.2024.130802.
DOI: https://doi.org/10.1016/j.jhydrol.2024.130802

Interpretive Summary: Soil freeze and thaw processes are responsible for soil-liquid and -gaseous transport driving and supporting a myriad of other physical, chemical and biological processes. The unfrozen or liquid water- and ice- contents that coexist in frozen soil are challenging to quantify, but are also critical for understanding these processes within soil. Various disciplines, such as engineering or soil, environmental and earth sciences, apply a variety of numerical modelling techniques and methods to determine or simulate unfrozen water content. Despite a global need for such understanding and tools, few studies have attempted to review and synthesize these works. We therefore collate and review currently available methods of determining unfrozen water and ice contents in soil. This review will be helpful to both experienced and novice researchers conducting work in freezing and thawing soils.

Technical Abstract: Soil freeze and thaw processes occur at cycles that can be diurnal, seasonal, annual, decadal and beyond. These cycles are responsible for soil-liquid and -gaseous transport driving and supporting a myriad of other physical, chemical and biological processes. The unfrozen or liquid water- and ice- contents that coexist in frozen soil are first of all challenging to quantify, but are also critical for understanding these processes within soil and porous media. Various disciplines, such as environmental and earth science or engineering, apply a variety of numerical modelling techniques and methods to determine or simulate unfrozen water content. Despite a global need for such understanding and tools, few studies have attempted to review and synthesize these works. The objective of this study was therefore to review and collate currently available methods of determining unfrozen water and ice contents. The review starts with a description of soil freezing and thawing processes and touches on the dominant impact factors. The principles, applications, advantages and limitations of miscellaneous methods for direct determination of unfrozen soil water are reviewed and categorized (e.g., tensiometer method, dilatometry, radioactive methods, electromagnetic methods, ultrasonic method, and thermal methods). In addition, indirect estimates of unfrozen water content using various models are also presented, based on frozen soil temperature (e.g., Clapeyron equation), specific surface area, soil water retention character and soil freezing character. At present, radioactive methods, electromagnetic methods and heat pulse technology are widely used in practice. We suggest that the combination of multiple methods (e.g., heat pulse and electromagnetic methods) is generally an improvement over the limitations of individual measurement approaches or instruments.