Numerical analyses of factors affecting the LNAPL source-zone architecture

The migration behavior and entrapment of light non-aqueous phase liquid (LNAPL) in subsurface media are influenced and controlled by a variety of factors. It is generally believed that LNAPL will pass through the vadose zone and transport to the water table after surface leakage. However, the heterogeneity of the subsurface medium and the variability of water content may lead to a complex LNAPL source-zone architecture. For example, LNAPL cannot reach the water table but accumulates in the capillary zone. In this paper, based on the numerical model, the effects of LNAPL leakage, medium heterogeneity and water content, changes in the water table on the LNAPL source-zone architecture are analysed. The results show that (1) LNAPL can transport to the water table when there is a large amount of leakage. (2) When the amount of leakage is small, LNAPL may accumulate on the edge of the capillary zone and may not reach the water table under the coarse-fine layered heterogeneous conditions. (3) The clay lens in the vadose zone is not always a hindrance to the migration of LNAPL. LNAPL can penetrate the clay lens with low water content, and only the clay lens with high water content can hinder the infiltration of LNAPL. (4) The periodic change in the water table can increase the polluted range.