No molecular diffusion and hydrodynamic dispersion in T2VOC
When modeling PCE transport process, it is necessary to consider the dispersion phenomena. However, in T2VOC module, there is no allowance for molecular diffusion in the aqueous and NAPL phases, or for hydrodynamic dispersion. Moreover, T2VOC is under conditions of local chemical equilibrium, the concentration of a compound in a phase is related to the concentration in another phase by a constant.
So I would like to know how can I explain the PCE tranpsort process, especially the variation of PCE concentrations in aqueous phase, under these assumption in T2VOC simulation. And is the key parameter in this process is 'SOLA' in the input file
I am not really an expert in T2VOC, so others may want to answer also, but if you want molecular diffusion in all phases, you should use TMVOC instead of T2VOC. In general, if PCE is dissolved in the aqueous phase, it will be transported by both diffusion and advection (that is, it will be carried along with aqueous phase flow), which could lead to variations of PCE concentration. You are correct that SOLA is the solubility of the species in the aqueous phase, if solubility is considered a constant. If solubility is temperature dependent, then you also need SOLB, SOLC, and SOLD, as explained in the User's Manual.