On the linear driving force model for sorption kinetics of organic compounds on suspended sediment particles

Sorption kinetics of hydrophobic organic compounds on suspended sediments i n the water column are analyzed using the linear driving force (LDF) model. The LDF model succinctly captures the different mass transfer resistances for uptake by aqueous suspended particles. The LDF model is appropriate for those situations where both water- and particle-side processes are importa nt. It is shown that departure from equilibrium sorption may be responsible for the near constancy in experimental sorption coefficients obtained for strongly hydrophobic compounds towards aqueous suspended particles in the s edimentary environment. The time to equilibrium for sorption diminishes wit h decreasing particle radius and increases with increasing compound hydroph obicity. For strongly hydrophobic compounds, the apparent partition coeffic ient is shown to be inversely proportional to the suspended solids concentr ation when sorption is far from equilibrium.