Abstract:In order to quantitatively study flow and solute migration in unsaturated zone-saturated zone under steady flow and unsteady flow, unsaturated zone-saturated zone was established based on theory of unsaturated zone and saturated zone flow and solute transport theory. The internal flow equation and contaminant transport model were modeled by Van Genuchten-Mualem model, and simulation calculation was performed and results were given based on Toughreact software. The simulation results show that in case of steady flow, flow rates of unsaturated zone and saturated zone are gradually reduced, and finally tend to be stable. In case of non-steady flow, initial phase of flow velocity is gradually reduced, and at the later stage, the flow velocity changes cyclically according to the quarterly precipitation. The different flow rates generally change periodically when total precipitation and other conditions are same, unsteady flow has a promoting effect on solute transport relative to steady flow, that is, its migration rate is faster, but the impact scale is not large. Over time, pollutants will enter the groundwater through vadose zone, with Na+ being the fastest, hexavalent chromium being the second, and uranium appearing the latest.