Quantification of the dissolved organic matter effect on the sorption of hydrophobic organic pollutant: application of an overall mechanistic sorption model

This study presents an overall sorption model to estimate the sorption equilibrium coefficients of hydrophobic organic pollutants for heterogeneous aquatic systems. This proposed model combines a series of sorption equilibrium relationships including the adsorption of dissolved organic matters on particulates, the binding between organic pollutants and dissolved organic matters, and the sorption of organic pollutants on particulates with or without the presence of dissolved organic matters. By using this model, variations among the sorption equilibrium coefficients with the concentrations of dissolved organic matters are obtained. Also discussed herein are case studies involving pollutants having a wide spectrum of K(ow)s, different types of dissolved organic matters, different pH values and ionic strengths. In most of the case studies, the sorption equilibrium coefficients initially increase with the-concentrations of dissolved organic matters and, then, decrease after reaching a maximum value. This study also addresses the relative errors of partition coefficients attributed to the negligence of the effect caused by the dissolved organic matter, the so-called third-phase effect.