Agricultural PM₁₀ emissions from cotton field disking in Las Cruces, NM

Various studies have shown a relationship between elevated levels of inhalable particulate matter (PM) and agricultural practices, especially in the vicinity of agricultural fields. Airborne particle concentrations and meteorological variables were measured during nine agricultural field events on a cotton field in Las Cruces, NM in March 2008. A variety of real-time and integrated PM₁₀ and total suspended particles (TSP) samplers were used during sampling. The field events were designed to measure particle concentrations at different heights, near (4 m) and far (20-100 m) from a disking tractor. Particle concentrations decreased with increasing distance from the ground for near-source disking events, whereas particle concentrations were almost independent of height for background events. Near-source disking event particle concentrations were 4-7 times higher than those for far-source disking and background events. Near-source disking events had PM₁₀ emission factors ranging from 78 to 239 mg m^-2, while those for far-source disking events ranged from 8 to 89 mg m^-2. PM₁₀ plume heights for near-source disking events were between 4 and 5.7 m, whereas those for far-source disking events were between 12 and 15 m. Meteorological variables were found to influence emission factors, with wind speed showing a nonlinear relationship with emission factors. No clear relationship was found between soil moisture content and emission factors probably because the range of soil moisture was small. Impactor data indicated 10-40% of the total mass of agricultural PM collected was less than 1 μm in diameter for the clay loam soil type. Vertical PM₁₀ concentration profiles showed maxima at sampling heights between 1 and 2 m above the ground.