地下水中轻质有机污染物(LNAPL)透镜体研究

Study on light non-aqueous phase liquid lens in subsurface water

在二维砂槽模型中模拟了轻质油在均匀多孔介质地下水非饱和区和饱和区中的运移过程。模拟结果表明 ,地下水毛细区是轻质油污染的重点区 ,除了 LNAPL 的残留以外 ,进入地下水饱和区中的 L NAPL 终将被地下水顶托回到毛细区中 ,毛细区以上的绝大多数 LNAPL 也将在重力作用下进入毛细区中 ,试验中观察到达到稳定状态时 LNAPL 透镜体的上边缘略微高出毛细区。利用多孔介质毛细管模型 ,建立了利用界面张力、接触角、介质特征孔隙直径等物理量估算不同位置 LNAPL 透镜体厚度及透镜体可能最大厚度的关系式 ,模型说明 ,由于毛细区中越靠近毛细区上边缘位置 ,油 -水界面上的压差越大 。

s:The movement of light oil(gasoline and kerosene)in subsurface homogeneous water saturated zone and water unsaturated zone were simulated in a twodimensional sand trough model.The simulation results showed that groundwater capillary zone is the key area that will be contaminated by LNAPLs.Except the residual part,LNAPL that enters groundwater saturated zone would be displaced back into capillary zone at last by groundwater,and most of LNAPL about the groundwater capillary zone would enter capillary zone too at last.It is observed in experiment that after the visible movement of LNAPL stopped the upper face horizontal spreading of LNAPL always developed along the top boundary of capillary zone.Based on capillary tube model of porous media,relationships of estimating the possible maximum thickness and the diameter of medium were developed.Considering lateral flow in porous media,a twodimensional capillary tube model was developed,comparison of pressure difference on LNAPLwater interface in horizontal direction showed that in capillary zone,higher the position of the interface was,larger the pressure difference was,this result could be used to explain why horizontal spreading of LNAPL always happened along the top boundary of capillary zone.