Pesticides are applied to agricultural fields to control unwanted pests but can volatilize and be transported downwind by wind currents to create the potential for non-target organism exposure. Volatilization rates change through the growing season due to pesticide application timing, meteorological differences, and the fraction and differential flux rates from soil and vegetation matrices. Field studies quantifying pesticide volatility are expensive and cannot capture the near semi-infinite possible parameter combinations of edaphic, crop, management and meteorological conditions encountered under regional agronomic practices. A numerical approach, used to simulate pesticide dissipation above and below ground to augment field/lab experiments, are coupled into a single numerical tool using the COMSOL Multiphysics® software package. Current emphasis focuses on pesticide volatility into air from soil/vegetation and resulting near field neighboring air concentrations. A comparison of simulations using an insecticide (chlorpyrifos) applied to potato and alfalfa fields shows good agreement (R2 0.68-0.98). Chlorpyrifos volatility from plant surfaces drives the overall volatility within the first several days post application. The maximum volatility flux rate simulated and observed were 0.79 mg m-2 s-1 and 0.66 mg m-2 s-1 for the alfalfa trial, and 2.72 mg m-2 s-1 and 2.17 mg m-2 s-1 for the potato field, respectively. This coupled multi-physics tool [computational fluid dynamics (CFD), mass transfer coefficients, and variably saturated flow in soil] can be used to estimate volatility flux rates of pesticides when little or no prior knowledge is available, and for extrapolating field study observations to different and diverse scenarios.

Predicting pesticide volatility through coupled above/below ground multiphysics modeling

254th National Meeting (2017)

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