Numerical simulation of groundwater contaminant transport in unsaturated flow

A sand-box experiment equipment is constructed to simulate the transportation of contaminant in unsaturated flow under dirichlet boundary condition. Based on analysis of the mechanism in unsaturated migration, taking a riverland as an example, the model of water quality which was affected by contaminant transport was built, and the calculation values coincided well with experimental data. The results showed that the lateral migration should not be neglected when seepage velocity was high. In addition, the lateral migration was faster in high moisture content areas and the solute was retained for a short time; however, the situation was reversed in low moisture content areas. Moreover, during the initial stage of solute transport, the velocity of the trailing end of the pinnate pollution zone was high under the effect of capillary action, which would lead to expansion of the range of pollution. Furthermore, the relative concentration curve of pollutants presented a single peak state, with the peak value of the curve increasing with the velocity, and the arrival time of the peak value was also gradually advanced. Therefore, this study can provide reference for the prediction and control of groundwater contaminant transport in an unsaturated zone.