Influence of groundwater flow velocity and geological heterogeneity on DNAPL migration in saturated porous media

The migration behavior and distribution of Dense Non-aqueous Phase Liquid (DNAPL) in subsurface is influenced by lots of factors including phys icochemical properties of DNAPL, leakage rate, groundwater flow velocity, and geological heterogeneity. This study investigates the influence of flow velocity and heterogeneity on DNAPL migration in the saturated zone. Heterogeneity is described by random permeability field based on geological statistical method, and migration processes of released DNAPL at varying groundwater flow velocity are simulated using T2VOC. The results show that enhanced flow velocity promotes both the lateral and vertical migration of DNAPL. In the cases of fixed flow velocity, increased heterogeneity leads to an increased spatial variability in morphology of DNAPL plume and percolation paths. DNAPL is captured in high permeabiliy zone and bypass flow around the low permeability zone. With increased standard deviation of log-permeability, the promotion effect on lateral DNAPL migration resulting from water flow is reduced when the direction of preferential pathway of DNAPL migration is opposite to water flow, inversely, the promotion effect is enhanced when these two directions are similar. The plume spread in the horizontal direction, and the spatial variability of both centroid (first moment) and variance (second moment) of plume, start position of DNAPL pool as well as pool length increase with synchronously increased flow velocity and heterogeneity. ©, 2015, Shuili Xuebao/Journal of Hydraulic Engineering. All right reserved.