Environmental Fate and Transport of Organic Contaminants in Soils at Waste Disposal Sites

Current approaches for describing the environmental dynamics of organic constituents in complex waste mixtures are reviewed. Factors controlling equilibrium and nonequilibrium sorption of organic contaminants from aqueous solutions are summarized, and extension of these concepts to predict the effects of mixed solvents are discussed. Presence of organic cosolvents increases solubility in a log-linear manner, leading to proportional decreases in sorption and retardation of nonpolar organic contaminants. Available data support the use of a log-linear cosolvency model and the UNIFAC model to predict the cosolvency effects. For predicting dissolution of aromatic hydrocarbons from multi-component organic liquid wastes, available data for gasolines, diesel fuels, and coal tars support the adequacy of approaches based on the assumption of ideal mixtures (Raoult's law). Examples
are presented where the cosolvency model and the Raoult's law approach were applied for designing remediation of contaminated soils at industrial waste disposal/spill sites and for predicting the concentrations of aromatic hydrocarbons in the leachate from a source area.