Estimation of Free-Product PCE Distribution in Thick Multilayered Aquifers as Possible Long-Term Pollution Sources for Shallow and Deep Groundwaters, Using High-Precision Numerical Simulations

Chlorinated organic compounds are Persistent Organic Pollutants (POPs) with high environmental continuity. These chemicals possess the ability to permeate into the environment across both unsaturated and saturated zones. This study examines the potential impact of perchloroethylene (PCE) releases in aquifer systems consisting of layers with varying permeability. The numerical simulations utilized the CactusHydro numerical code that employs a high-resolution shock-capturing flux conservative method to solve the non-linear partial differential equations of a three-phase immiscible fluid flow and study the migration of PCE into variably saturated zones to predict the spatial and temporal distribution of free products across multilayered aquifers. Two scenarios were simulated to predict how a first low-permeable horizon would affect the downward migration of PCE in its pure phase. The numerical simulations show that the multilayered aquifer system is vulnerable to an in-depth study of the PCE migration paths in the pure phase. However, very long times (about a year) are required for the DNAPL to be able to cross the semi-permeable horizons. The results in both scenarios show the quantity of mass (in kg and percentage concerning the initial one) that is left along the multilayered aquifer during the migration and after several years.