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 were coincided well with experimental data. The results showed that the lateral migration should not be neglected when the seepage velocity was high. In addition, the lateral migration was faster in high moisture content area and the solute was retained for a short time, however, the situation was reverse in low moisture content area. Moreover, during initial stage of solute transport, the velocity of the trailing end of pinnate pollution zone was high under the effect of capillary action, which would lead to expand the range of pollution. Furthermore, the relative concentration curve of pollutants presented a single peak state, which the peak value of the curve increased 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 unsaturated zone.
The characteristics of contaminant transport in unsaturated groundwater are explored.
Water content and lateral migration velocity affect the retention time of solute.
The relative concentration curve is an unsymmetrical single peak curve with obvious trailing phenomenon.
The velocity of the trailing end of pinnate pollution zone was high during initial stage of solute transport.