降雨蒸发条件下渗流区污染物迁移的数值模拟

Numerical simulation of contaminant transport in vadose zone during rainfall and evaporation

采用溶质传递方程和水流动方程联立耦合进行数值求解,模拟土壤渗流区中有机污染物的垂直一维迁移过程。传递方程综合考虑气相扩散和液相的对流扩散过程,并且在水流动方程的边界条件中包含有降雨、蒸发的气候条件。数值模拟过程中将有机污染物苯作为研究对象,采用美国加州地区实际的土壤物性数据和气候条件,得到的模拟结果和Grifoll的研究结果基本一致。实验结果显示500 h污染物到达的深度近似为125 cm,2 000 h已经达到180 cm。另外,在模拟区域的不同深度设置数值模拟数据采集点,结果发现越接近不饱和区上表面的地方,受气候边界条件影响越大。

Transport of organic chemicals in soil vadose zone was simulated by using a coupling model of solute transport and water flow. In the solute transport equation, convective-dispersive transfer in liquid phase and diffusion in gas phase were considered. Furthermore, the effects of climatic conditions on transport were included in the boundary conditions of the governing equations. Benzene was selected as a contaminant and the data on the characteristics of a loam soil and climatic conditions in Southern California were introduced in the modeling. The results of numerical experimentation were compared with those from a study of Grifoll and this comparison shows that there was a good agreement between the two studies. The results show that the solute reaches a depth of about 125 cm after 500 h, almost 180 cm after 2 000 h. Five observation points were set at different depths, which reveal that the solute transport and water content in surface layer are significantly impacted by the dynamics of rainfall.