Environmental Studies: Air Quality
Project Period: March 2010 - May 2013
Particulate matter (PM) of aerodynamic diameter less than or equal to 10 µm (PM₁₀) is regulated by the U.S. Environmental Protection Agency (EPA) as part of the National Ambient Air Quality Standards (NAAQS). This article reports on the calibration and evaluation of the HYSPLIT (Hybrid Single‐Particle Lagrangian Integrated Trajectory) version 4.9 model to simulate regional dust dispersion from a disking operation. Disking operations in a cotton field in Las Cruces, New Mexico, were conducted, and boundary layer PM₁₀ concentrations were sampled using a DustTrak sampler on an airplane flown at altitudes between 200 and 500 m and several kilometers downwind. Using North American Mesoscale (NAM) forecast meteorological data (NAM12km, 12 km resolution) with vertical profiles, the model is capable of reasonably simulating regional PM₁₀ dispersion (simulated data = 1.048 × measured data with R² = 0.85).
Dust emission factors for regional- and local-scale simulations of particulate matter with diameters less than or equal to 10 µm (PM₁₀) dispersion from agricultural operations are not generally available. This article presents a modification of the U.S. Environmental Protection Agency AP-42 approach to better calculate aerosol emission factors of PM₁₀ for agricultural tilling operations. For the modification, we added the variables soil moisture, operation type, and crop type based on experimental and literature data to estimate local emission factors. Field experiments to measure the PM₁₀ emissions from rolling, disking, listing, planting, and harvesting cotton (Gossypium hirsutum L.) were conducted. Data from these field experiments plus literature data were used to isolate the effects of soil moisture and operation type on the emissions. Literature data were then used to add different crop and operation types.