Department of Hydraulics Transportations and Roads, Sapienza University of Rome-Via Eudossiana 18-I-00184-Rome, Italy.
J Hazard Mater. 2010 Apr 15;176(1-3):1006-17. doi: 10.1016/j.jhazmat.2009.11.141. Epub 2009 Dec 3.
Laboratory experiments have been carried out with and without groundwater flow in a two-dimensional laboratory-scale tank to assess the influence of layered media and hydraulic gradient on DNAPL infiltration and redistribution processes. Hydrofluoroether has been used as DNAPL and glass beads have been utilized as porous medium. An image analysis procedure has been used to determine saturation distribution during infiltration and redistribution processes. This method allows quantitative time dependent full fields mapping of the DNAPL saturation, as well as the monitoring of DNAPL saturation variation. By means of performed experiments important information were obtained about the migration and redistribution process, the infiltration and migration velocity, the characteristics of migration body. The experimental results show that the hydraulic gradient promotes the infiltration process, increasing the infiltration rate. It hampers DNAPL spread and fingering bringing to a reduction of residual DNAPL and it also promotes the DNAPL redistribution, and it reduces the amount remaining at residual saturation. Furthermore the hydraulic gradient promotes downward and down-gradient migration. DNAPL migration in the direction of water flow, can be considered important due to significant errors in the location of sources in the case of high gradients and high aquifer thicknesses, and for high water flow velocities, such as those which can be expected during pumping actions in water supply or in remediation activities.
实验室实验在二维实验室规模的水槽中进行，有无地下水流动，以评估层状介质和水力梯度对 DNAPL 渗透和再分布过程的影响。氢氟醚被用作 DNAPL，玻璃珠被用作多孔介质。使用图像分析程序来确定渗透和再分布过程中的饱和度分布。这种方法允许对 DNAPL 饱和度进行定量的、随时间变化的全场映射，以及监测 DNAPL 饱和度的变化。通过进行的实验，获得了有关迁移和再分布过程、渗透和迁移速度、迁移体特征的重要信息。实验结果表明，水力梯度促进了渗透过程，提高了渗透速率。它阻碍了 DNAPL 的扩散和指进，导致残余 DNAPL 减少，同时促进了 DNAPL 的再分布，减少了残余饱和度下的残留量。此外，水力梯度促进向下和向下梯度迁移。在高梯度和高含水层厚度的情况下，以及在高水流速度（如在供水或修复活动中的抽吸作用期间可能预期的速度）下，由于在源位置的重大误差，DNAPL 沿水流方向的迁移可能被认为是重要的。
