The dispersion mechanism of dispersive seasonally frozen soil in western Jilin Province

摘要

A large area of soda-saline soil has developed in the seasonally frozen area of western Jilin Province, northeast China. Because of the strong dispersibility of this soil, irrigation channels and other water conservation projects are often damaged or even destroyed by erosion. In this study, grey relational analysis was used to analyze the correlation between the physicochemical properties and dispersibility of the soil and thus reveal the dispersion mechanism. Moreover, the effects of salt migration and microstructural changes on soil dispersion in the seasonally frozen area were studied via a water migration simulation experiment with samples from western Jilin Province. The high cation exchange capacity, high exchangeable sodium percentage, high pH, low organic matter content, and low clay content of the soil were the main factors contributing to soil dispersion. In addition, in winter, salt in the soil constantly moved from the lower non-frozen soil layer to the upper frozen soil layer along with water. After the frozen soil layer thawed in spring, the evaporation of water at the soil surface caused the salt to continuously migrate to the surface along with the water. As a result, the sodium ion content in the surface soil increased considerably thereby enhancing soil dispersibility. However, frost heave increased the distance between soil particles, weakened the structural connection among soil particles, and loosened the soil particles. Therefore, the seasonal freeze-thaw process in the study area promoted soil dispersion. This study has a certain theoretical significance for the construction of water conservancy projects and soil improvement.