Construction and verification of a calculation model for unfrozen water in sodium sulfate saline soil

Abstract

[Objective] Salt crystallization in saline soil absorbs water, leading to changes in unfrozen water content. To investigate the effect of sodium sulfate on the unfrozen water content in saline soils with higher salt content. [Methods] A systematic laboratory experiment was conducted to study the influence of factors such as temperature, initial water content, soil type, and salt content on the unfrozen water content. A model for unfrozen water under different salt content conditions was constructed based on the principle of mass conservation. [Results] The result showed that under the same water content conditions, the higher the salt content, the lower the unfrozen water content in saline soil when the temperature reached the freezing point. Under the same negative temperature conditions, the unfrozen water content in the freezing process was higher than in the melting process. Furthermore, a hysteresis was observed in the change in unfrozen water content with temperature during the freezing and thawing process. [Conclusion] The constructed model for predicting unfrozen water content considers the salt crystallization stage and the ice-salt eutectic stage and quantifies the water released by salt crystallization, making it more suitable for predicting the unfrozen water content in high-salt saline soils. This provides scientific support for agricultural development and engineering construction in the cold and arid regions of Northwest China.

Keywords

sodium sulfate saline soil / unfrozen water / solubility / salt crystallization / influence factors