Response of Solute Migration to Different Factors under Unidirectional Freezing in Sandy Soil

Abstract

Owing to the scarcity of land resources, the rational development and use of frozen soil resources and solutions to frozen soil disasters are essential. In this study, an indoor one-dimensional soil column simulation test was conducted under unidirectional freezing conditions. The temperature, water content, and conductivity of the sand were monitored using a time-domain reflectometer (TDR), and a mathematical model to analyze the relationships among solute concentration, temperature, and conductivity was established, to convert the conductivity into soil solute concentration. Then, the sodium chloride solute redistribution in soil under different soil densities (1.23 and 1.40 g/cm3), initial water contents (10% and 13%), freezing temperatures (−20°C and −35°C), and salt concentrations (0.2 and 0.3 mol/L) was analyzed. The results show that solute concentration and temperature are the two factors that affect conductivity. The relationship between conductivity and solute concentration can be used to quantitatively analyze the solute changes in soil. The soil density, initial water content, freezing temperature, and solute concentration affect solute migration under unidirectional freezing conditions. The solute migration efficiency decreases with increasing soil density and initial water content and increases with decreasing freezing temperature and increasing solute concentration. In this study, the aim was to further understand the mechanism through which solute migration occurs in frozen soil, to provide theoretical support for the rational exploitation and use of resources, the prevention and control of soil pollution, and the promotion of agricultural development in cold regions. These results provide theoretical support for soil water and salt simulations, pollution control, and agricultural development in cold regions.