Multiphase transport of organic chemical contaminants in the subsurface

A theoretical study of multiphase contaminant transport in shallow subsurface systems has been conducted. This work is based in large part on the results of numerical simulations performed using two numerical simulators developed for modeling contaminant transport problems involving nonaqueous phase liquids (NAPLs).;An investigation of factors affecting the gas phase transport of evaporating organic liquids in the unsaturated zone is presented. A numerical simulator, TOUGH VOC, is developed for the purpose of modeling the isothermal evaporation and gas phase transport of NAPLs in the unsaturated zone. Numerical simulations using a two-dimensional cylindrical geometry and including the effects of phase partitioning between the solid, gas, water, and NAPL show that mass transfer due to density-driven flow may dominate the gas phase transport of some organic chemical vapors in the unsaturated zone.;A numerical simulator, STMVOC, is developed for modeling steam displacement of NAPLs in shallow subsurface systems. This three-dimensional simulator models true three phase flow with heat transfer, and equilibrium interphase mass transfer of the organic chemical component between each of the phases. The simulator is validated in part by simulations of one-dimensional laboratory scale steam injection experiments. The numerical results are in good quantitative agreement with the experimental results in each case.;Several one-dimensional numerical simulations of the steam displacement of high boiling point NAPLs are presented. The results of these simulations are consistent with predictions made using an analytically derived necessary condition for efficient high boiling point NAPL removal by steam.;To further validate the numerical simulator, a series of two-dimensional laboratory scale steam injection experiments are simulated. The numerical results for each case are in satisfactory qualitative agreement with the experimental results. Several hypothetical simulations of two-dimensional steam displacement of xylene at different scales are presented. These simulations suggest that if the ratio of gravitational to viscous forces is the same in each case, that laboratory scale experiments will be fairly representative of field scale steam displacement processes.