Modeling evaporation dynamics from soils with major chlorides and high salinity

Evaporation from saline soils is a crucial process with wide-ranging implications for diverse sectors, such as civil engineering, agriculture, and the global hydrological cycle. This study conducted soil column experiments to investigate salt precipitation of four major chlorides (NaCl, KCl, CaCl₂ and MgCl₂), and their effects on soil evaporation as compared with the control (CK) of distilled water. Results indicate that NaCl and KCl (Class Ⅰ) tend to precipitate as efflorescent salt crust, whereas CaCl₂ and MgCl₂ (Class Ⅱ) precipitate beneath the soil surface, forming subflorescence. A numerical model was then developed to simulate soil evaporation of saline solutions (SSE) based on idealized cylindrical capillary pathways, which considers efflorescent and subflorescent salt precipitation patterns and their impact on evaporation. This model was integrated in the vertical one-dimensional soil water and flow solute transport model (LAWSTAC) to improve the accuracy for CaCl₂ and CK treatments, resulting in the modified SSE (MSSE) model. The MSSE model demonstrated improved simulation accuracy for CaCl₂ and CK treatments, reducing the mean relative errors (MREs) of simulated versus measured evaporation rates by 34.4% and 6.6%, increasing the coefficients of determination (R²) by 0.07 and 0.25, and improving the Nash-Sutcliffe efficiency coefficients (NSEs) by 0.04 and 0.30, respectively. Results of spatial and temporal distribution of soil water and various solutes simulated by the MSSE model further support its reliability, especially for soils with high salinity of chloride. Scenario simulations with varying chlorides, concentrations, and soil textures indicate that coarse-textured soils are at higher risk of salinization and monitoring the concentration and composition of external saline water is essential for soil salinization control.