Freezing and thawing characteristics of saline farmland soils: analysis of hydrothermal parameters and driving mechanism

Overview

This study quantifies the spatiotemporal dynamics of coupled water-heat-salt processes in saline farmland soils subjected to seasonal freeze-thaw cycles under field conditions in northern China. The investigation integrates continuous in-situ monitoring with controlled laboratory experiments to characterize hydrothermal parameter responses and elucidate mechanisms governing water and salt redistribution during freezing and thawing phases.

Methods and approach

Systematic monitoring was conducted in a representative saline agricultural field in northern China through hourly in-situ measurements combined with complementary laboratory freeze-thaw experiments. Field observations captured natural seasonal transitions, while controlled experiments enabled precise quantification of key hydrothermal parameters including water retention characteristics, relative permeability, thermal conductivity, and volumetric heat capacity across soil profiles at different depths. Soil temperature gradients and matrix potential gradients were measured to characterize driving mechanisms of water-salt migration.

Results

Air temperature and snow cover induced vertical differentiation in heat and mass transfer. Water content in shallow soils increased by 32.20% relative to early winter due to water retention in frozen soil and snow, whereas snowmelt infiltration reduced salt content by 15.44-34.02%. During freezing, relative permeability decreased by up to eight orders of magnitude in surface layers and three orders of magnitude in deeper layers; post-thaw permeability exceeded pre-freeze values. Thermal conductivity increased by 20.76-56.78% while volumetric heat capacity decreased by 22.30-39.41%, generating asymmetric cooling and warming rates with net heat loss. Soil temperature gradients (maximum 0.775°C/cm) and matrix potential gradients (maximum 134.9) in shallow soils were 9-10 and 3-4 times higher, respectively, than in deeper layers, with both parameters oriented toward the cold end and driving water-salt migration.

Implications

The quantified responses of hydrothermal parameters establish empirical relationships essential for parameterized modeling of freeze-thaw processes in saline soils. The documented asymmetry between thermal conductivity and volumetric heat capacity changes elucidates why freezing induces greater water accumulation and salt redistribution than thawing, with implications for predicting soil water availability and salt accumulation patterns in seasonal frost regions. The primary and secondary contributions of soil temperature gradients and matrix potential gradients provide a mechanistic framework for assessing water-salt evolution in comparable saline agricultural systems, supporting quantitative prediction of long-term soil degradation and remediation potential.

Disclosure

• Research title: Freezing and thawing characteristics of saline farmland soils: analysis of hydrothermal parameters and driving mechanism
• Authors: Dongmei Ruan, Jianmin Bian, Yu Wang, Zhiqi Gu
• Publication date: 2026-02-21
• DOI: https://doi.org/10.1007/s12665-026-12847-y
• OpenAlex record: View
• PDF: Download
• Image credit: Photo by wal_ 172619 on Pexels (Source • License)
• Disclosure: This post was generated by artificial intelligence. The original authors did not write or review this post.