Development of a Multimedia Model for the Fate Prediction of Hydrocarbon Fluids in Agrochemical Formulations

Hydrocarbon (HC) fluids are effective inerts in pesticide formulations. These fluids consist of volatile organic compounds (VOCs) that are assumed to be completely volatilized and undergo subsequent atmospheric reaction that may contribute to ozone formation during field use. However, these assumptions are based on laboratory evaporation tests, which fail to account for other environmentally relevant and competitive fate processes, such as biodegradation, soil sorption, runoff, and leaching. If appropriate input parameters are known, or can be reliably estimated, mass balance multimedia models can be used to characterize the importance and uncertainty of various fate processes and provide a more realistic assessment of the potential contribution to ozone formation. A model has been developed and applied to an agricultural field application scenario. Preliminary results suggest biodegradation and soil sorption are significant fate processes that can reduce the mass of HC VOCs entering the atmosphere by volatilization. The implications of applying multimedia models in assessing potential ozone formation from HC fluids in agricultural uses are further highlighted and preliminary laboratory work to confirm model findings is also discussed.