The soil properties are uniform from the soil surface to the bottom of the treatment zone. This assumption will rarely, if ever, be met in the field. The user can estimate the impact of non-uniform soils by comparing results for several simulations covering the range of soil properties present at the site. The flux of water is uniform throughout the treatment site and throughout time. This assumption will rarely be met in the field.
Hydrodynamic dispersion is insignificant and can be neglected.
This assumption gives rise to sharp leading and trailing edges in the pollutant slug. These sharp fronts will not exist in soils. As a result, the pollutant will likely reach any depth in the treatment zone before the time predicted and it will remain at that depth longer than predicted by the model. Linear isotherms describe the partitioning of the pollutant between the liquid, soil, vapor, and oil phases. Local equilibrium between phases is assumed.