Modelling agrochemical dissipation in surface microlayers following aerial deposition

Conventional chemical fate models which treat the water compartment as being well-mixed may not adequately describe the fate of chemicals deposited onto lakes and ponds from aerial applications or spray drift. The Quantitative Water Air Sediment Film Interaction (QWASFI) model is developed here to predict agrochemical dissipation in surface microlayers or films following aerial deposition on to natural waters. The model was applied to four pesticides: bromoxynil octanoate, cypermethrin, deltamethrin and fenitrothion, from five previously published studies. QWASFI provided a more accurate description of processes, and improved quantification of concentrations than a model which does not address the effects of the film compartment.