| Many ground water contamination problems originate from sites contaminated with complex waste mixtures. Complex waste mixtures of environmental concern studied here are multi-component, organic immiscible liquids, such as coal tar. The release and transport of organic chemicals in saturated media contaminated with such complex waste mixtures are controlled by two major processes: dissolution and sorption. These processes were discussed at a mechanistic level, in relation to their impact on contamination and remediation of soils and aquifer media.; A model was developed, based on Raoult's law, for describing multi-component dissolution from complex waste mixtures under equilibrium and nonequilibrium conditions. Model simulations and experimental data showed that with depletion of more-soluble components, the concentration of all other constituents increases due to changes in mole fraction. Nonideal conditions also increase contaminant concentrations, but can generally be ignored at the field scale.; Rate-limited sorption of nonpolar organic compounds is controlled by two possible mechanisms: intra-organic matter diffusion and retarded intra-particle diffusion. Several models that describe sorption nonequilibrium, based on different conceptualizations of sorption dynamics, were discussed. The theoretical and experimental basis for the reported log-log, inverse, linear relationship between the first-order, mass-transfer rate coefficient and equilibrium sorption coefficient, which can be used to predict local-scale nonequilibrium, was critically evaluated. Sorption rates measured for three different contaminated matrices revealed that mass-transfer rates for some complex wastes may be significantly smaller than those observed for natural sorbents.; Cosolvents enhance the solubility, reduce sorption, and enhance the rate of approach to sorption equilibrium. Such effects have an important impact on the release and transport of organic contaminants when cosolvents are present at the waste-disposal site, or are introduced as part of a site remediation strategy. The cosolvency theory was used to develop several predictive models, which were used to evaluate solvent flushing as a potential remediation technique. |
