Modeling of the gaseous diffusion coefficient in the presence of NAPL

Gas phase diffusional resistance (D0/D) was measured using packed soil columns containing a fixed relative saturation of dodecane with varying moisture contents. Argon was chosen to serve as an inert gas phase tracer. Dodecane was used to simulate an immobilized NAPL in the soil subsurface. Results indicated that filling of soil pores by either liquid water or liquid dodecane has a similar effect on the gas phase diffusional resistance. A previously developed diffusion model was modified to account for total liquid (water and NAPL) saturation and compared with the experimental data.