Two-stage soil column experiments involving capillary rise and evaporation were conducted to improve understanding of salt and water movement from groundwater to soil surface. In total, 64 soil columns were placed in a tank partly filled with water in order to mimic the groundwater table in soil. Each soil column was analysed by dividing it into 27 segments to analyse pore water and ion distribution in both liquid and solid phases after prescribed time periods. The water and solute transport behaviour in the columns was simulated by a one-dimensional numerical model. The model considers the cation exchange of four cations (Ca2+, Mg2+, Na+ and K+) in both dissolved and exchangeable forms and anion retardation for one anion (SO42-). The Cl- is treated as a conservative solute without retardation. The numerical results of the cation distributions in both liquid and solid phases, anions in the liquid phase, and volumetric water contents were in relatively good agreement with the experimental results. To achieve a better model fit to these experimental results, a variable cation exchange capacity (CEC) distribution may be required. When a simple calculation scheme for evaporation intensity was applied, better predictions in terms of daily variation were achieved. The soil water profile displayed a steady state behaviour approximately 10 days after the start of the experiments. This was in agreement with numerical results and calculated distribution of velocity vectors. The final model includes cation exchange, anion retardation, and unsaturated water flow. Consequently, the model can be applied to study sequential irrigation effects on salt accumulation or reactive transport during major ion concentration changes in groundwater.
All Science Journal Classification (ASJC) codes
- Water Science and Technology