Desorption during resuspension events: kinetic v. equilibrium model

The spills and release of hydrophobic organic chemicals (HOCs) into waterbodies have resulted in the contamination of bottom sediments. When these sediments are resuspended by runoff events or by dredging, particulate-phase contaminants desorb to the water phase. Equilibrium between the particulate phase and the dissolved phase is usually assumed for most modelling applications regardless of time scale. This study compared predicted suspension times for sediments of various sizes with expected equilibration times for desorption. This comparison indicates that the equilibrium assumption is not valid for a wide range of parameter values typical of natural systems. In particular, compounds with high partition coefficients, greater than about 10⁴ mL g^-1, will have minimum equilibration times of at least one to ten days. This is likely to be greater than the expected resuspension time. -from Authors