Modeling atmospheric dispersion of pesticide particles in Yuma County

Sunyi Yuan1, Avelino F. Arellano1
1Department of Hydrology and Atmospheric Sciences, University of Arizona

Pesticide particles pose a risk to public health, especially when dispersed from areas having intensive agricultural activities to population centers. Here, we investigate the transport and deposition of these particles from pesticide applications on agriculture fields in Yuma County, Arizona. We use CALPUFF, which is an EPA-supported atmospheric dispersion program, to simulate the time- and space- varying dispersion of these particles. 11 pesticide applications on 19 sites in September and October 2011, were simulated. We configure CALPUFF within an ensemble framework by incorporating uncertainties in key parameters that control concentration downwind. In particular, we conduct ensemble simulations by perturbing emissions, chemical lifetimes, and deposition rates, application height, as well as key meteorological inputs (e.g., wind, temperature) in CALPUFF. Windrose pattern of September 2011 shows that south wind has a very high proportion, which means the pesticide particles are likely to go northward. Generally, during the period of 3 to 4 hours after each application, pesticide concentrations in certain areas exceeded the Texas effect screening level (0.1 〖μg/m〗^3). Current model results show that the particles’ deposition properties (geometric mass median diameter) have a big impact on the final results. When the particles’ geometric mass median diameters are set above 0.2 μm, more than 67% of the pesticide particles will be deposited in the domain (100×100km), others will be transported farther. Keeping the particles’ sizes bigger than 0.5 μm will help control the range of transport for the particles and the concentrations will drop more rapidly so that the risk for the residents can be much smaller. More strategies on mitigating the exposure to pesticide particles will be explored.

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