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An assessment of the dissolution rates of trichloroethylene (TCE) in glass bead, mixed sand and treated soil porous media reveals that there were trace TCE remaining in the soil and that the remaining TCE was sorbed into the porous medium. Porous media containing the compound at residual saturation were flushed with water and controls that include column design and experimental methods aimed at reducing the effect of column materials on effluent concentrations.

Hot water flooding was not effective in remediating a porous medium containing the nonaqueous phase liquid (NAPL) tetrachlorethylene. The method, used at different temperatures, was found to have only a 7% effect on interfacial tension at the NAPL interface and thus a minor effect for mass transfer. However, hot water flooding could be useful if temperature increases have a significant effect on a contaminant's aqueous phase solubility.

Surfactants have been shown to enhance the removal of nonaqueous phase liquids (NAPLs) during subsurface remediation by increasing their solubility in the displacing fluid. In a study investigating the dissolution of solid phenanthrene into solutions containing nonionic surfactants, steady-state phenanthrene effluent concentrations declined. In the absence of surfactant, measured values of effluent concentrations were consistent with experimental values, and increased with increasing surfactant concentrations. A mechanistic model describing the influence of surfactants on phenanthrene dissolution is presented.

Dense nonaqueous phase liquids (DNAPLs) prevent remediation of contaminated aquifers by preventing the solubilization and mobilization of residual NAPL. A new method that increases the efficiency of NAPL removal and surfactant recovery involves the use of nonionic surfactants such as Triton X-100. The technology promotes the removal of residual NAPL by improving macroemulsion transport. Mathematic models describing the technology are included.

The effectiveness of cosolvents in removing dense nonaqueous phase liquids (DNAPLs) at residual saturation within porous media is evaluated. The results showed that methanol flushing caused the mobilization, non-equilibrium dissolution and flow bypassing of tetrachloroethylene. Small-scale heterogeneities can lead to high residual DNAPL saturations which lend themselves easily to mobilization.

A general model for describing the heterogeneity of sorption parameters of natural systems was developed. It is shown that multiple-particle class models are more accurate in describing long-term sorption as compared to single-particle techniques. Model parameters were sensitive to the range over which data was collected. Tortuosity factors were in good agreement with theoretically derived values.

Two classes of sorption rate models are developed to address problems associated with existing models of the sorption process. The first, which is based on a generalized multiple domain paradigm, incorporates heterogeneities into current deterministic models. The second is stochastic in nature and as such characterizes sorption equilibrium and rate properties as continuous distributed random variables. The 16 formulated models are also compared to a data set on a sorption rate experiment involving a herbicide.

Several theories on the cause of desorption hysteresis have been developed. A diffusion and reaction model was used to interpret the results of experiments on sorption-desorption and the abiotic degradation of the solute lindane in a subsurface sand material. The results indicated that marked hysteresis was present. A surface-diffusion model suggested that the hysteresis was caused by slow rates of sorption-desorption.

Weber and Huang failed to discuss the limitations of the approach that they used to describe the solute phase distribution of phenanthrene in solution. The approach was based on Freundlich model parameters, Kf and n, for estimating the solute phase distribution relationship between aqueous phenanthrene and phenanthrene sorbed to solid materials. Some clarifications on the sorption processes that were modeled using the approach are discussed.

Develops a general modeling approach to account for heterogeneity of sorption parameters expected for natural systems and compares sorption rate descriptions of experimental data obtained with models that account for heterogeneity with traditional approaches. Comparison of effective tortuosity factors; Background and procedure followed; Modeling method; Results and discussion.

Presents a formulation of a set of deterministic and stochastic models to describe the sorption rates in subsurface systems. Comparison for sorption of diuron on a natural solid material; Equilibrium and rate data; Parameter estimation.