ABSTRACT
This chapter presents a summary of the model with various boundary and initial conditions with notes regarding their numerical evaluation. It discusses a detailed development of the model equations. In such a system, the presence of the denser liquid phase maintains high concentration gradients far longer than would be observed in a homogeneous vapor phase. A basic model involving pseudo steady-state diffusion from a receding liquid front is used to describe the system behavior. Air emissions from petroleum waste sites have been predicted using such models. Assuming the limiting step in the evaporation of a nonaqueous phase liquid from a sediment bed is the downward movement of the vaporizing liquid front. Thus the nonaqueous phase is modelled as pseudo steady-state vapor diffusion through the sediment, from a receding liquid front.
