Modeling PM10 regional transport from disking operations

Particulate matter (PM) of aerodynamic diameter less than or equal to 10 microns, PM10, is regulated by the U.S. Environmental Protection Agency (EPA) as part of the National Ambient Air Quality Standards (NAAQS). PM10 emitted from agricultural field operations (e.g., disking, listing, leveling, planting, harvesting) can be dispersed downwind in the far-field (i.e., > 1 km). This paper reports on the calibration and evaluation of the Hysplit4 (Hybrid Single-Particle Lagrangian Integrated Trajectory) model to simulate regional dust dispersion from a disking operation. Disking operations in a cotton field at Las Cruces, NM, were conducted, and boundary layer PM 10 concentrations were sampled using a Dustrack™ sampler on an airplane flown at altitudes between 200 m and 550 m and downwind several kilometers. Based on the measured data, the model parameters of released particle number, grid size, and particle release height were calibrated. Using NAM 12km meteorological data with vertical profiles, the model is capable of reasonably simulating regional PMlO dispersion (the simulated data =1.04 8xmeasured data with R²=0.85) when the PM10 was released at ground level. However, using measured point meteorological data at ground level and when the simulated particles were released at ground level, the model error was 90%. The smaller simulated values may be caused by the model's inability to capture the surface layer micrometeorology that transports ground-level dusts to higher altitudes. When using ground measurements of meteorological data, different release heights (50, 100, 150, and 200 m) of the particles were tested, and at the release height of 200 m (top of surface layer), the model performance was the best - the error was 10%, and the R² was 0.65.