Dissolution of residual tetrachloroethylene in fractional wettability porous media: correlation development and application

This work explores the dissolution behavior of residual tetrachloroethylene (PCE) in chemically heterogeneous soils. A numerical solute transport simu lator, that incorporates rate-limited dissolution and desorption using line ar driving force expressions, was developed and applied to analyze soil col umn dissolution data and to conduct numerical dissolution experiments. Publ ished mass transfer coefficients were unable to accurately predict the obse rved dissolution of entrapped PCE in fractional wettability porous media (m edia containing both water- and PCE-wet solid surfaces). A two-parameter po wer function expression for the lumped mass transfer coefficient was develo ped and successfully fit to these data. Correlations were then developed fo r the fitted mass transfer model parameters as a function of wettability an d grain size distribution characteristics. The power function model: in con junction with the parameter correlations, yielded reasonable predictions fo r long-term dissolution behavior in the more PCE-wetting media. Poorer pred ictions for the more water-wet materials were attributed to an increased se nsitivity of effluent concentration behavior to temporal changes in PCE sat uration in these systems. Many of the effluent concentration curves exhibit ed low and persistent concentration tailing after recovery of the separate phase PCE. This tailing behavior could be adequately modeled by incorporati on of rate-limited desorption. Results from numerical experiments indicate that both the magnitude and spatial distribution of wettability can signifi cantly influence PCE dissolution behavior and remediation time. (C) 2000 El sevier Science B.V. All rights reserved.