Modeling Irreversible Sorption of Hydrophobic Organic Contaminants in Natural Sediments

Abstract

The ability to quantitatively predict the resistant release of sediment-associated hydrophobic organic contaminants is extremely important in managing contaminated sediments. Many laboratory and field observations support the irreversible sorption model proposed by the authors, in which irreversible sorption is attributed to the physical binding of organic molecules in sediment organic matter. This kind of physical binding is not affected by a number of physical and chemical changes in the environment, such as competitive sorption, discharge of caustic materials, and external mechanical disturbance. Quantitatively, irreversible sorption of hydrophobic organic contaminants can be well modeled with an irreversible sorption isotherm, which accounts for the contribution of both the reversible and irreversible compartments. Since the parameters of the irreversible isotherm can be readily estimated or measured, it provides a simple yet more accurate approach to predicting the long-term resistant release of contaminants sorbed in sediments. The irreversible sorption model may significantly improve the accuracy of fate-transport modeling and risk assessment. It should also provide guidance to environmental decision making.