稳定流与非稳定流情况下非饱和—饱和区域重金属运移模拟

Simulation of Heavy Metal Transport in Unsaturated-Saturated Regions with Steady Flow and Unsteady Flow

为定量研究稳定流与非稳定流情况下非饱和带—饱和区域内水流及溶质迁移过程,在非饱和带及饱和区域流动理论及溶质运移理论基础上,建立了非饱和带—饱和区域内水流方程与污染物运移模型,采用Van Genuchten-Mualem模型来描述相对渗透率函数,基于Toughreact软件对模型进行模拟计算并给出模拟结果。模拟结果得出:在稳定流情况下,非饱和带及饱和区域流速均逐渐减小,最后趋于稳定;而非稳定流情况下,流速初始阶段逐渐减小,后期随着各季度降水量的不同流速大体呈周期性变化。在总降水量相同及其他条件相同的情况下,非稳定流相对于稳定流对溶质运移存在促进作用,即其运移速率更快,但影响尺度不大;随着时间的推移,污染物将透过包气带进入地下水中,其中钠离子最快,六价铬次之,铀出现最晚。

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.