Analysis of atmospheric particles on filters and mesquite leaves in El Paso and Phoenix (Texas, Arizonia)

Inorganic atmospheric particles were analyzed from two projects: particles from ambient air collected on polycarbonate filters in El Paso, Texas, and particles deposited on mesquite leaves in Phoenix, Arizona. Individual-particle compositions, sizes, and concentrations were determined with an automated electron microprobe and a scanning electron microscope. Multivariate statistical methods were used to classify the particles by composition.; Atmospheric particles collected in El Paso were analyzed in order to characterize the particles and identify general source locations. The four most abundant particle types, in order of abundance, were rich in calcium, sulfur, silicon, and copper. The sulfur-rich particles were most abundant at the beginning of the sampling campaign, when rain was present in the area. The calcium- and silicon-rich particles had the highest concentrations later in the sampling period, when the rain had passed. The copper-rich particles showed high concentrations during both periods. The calcium-, silicon-, and copper-rich particles originated locally, while the sulfur-rich particles appeared to be transported into the sampling area from distant sources.; Atmospheric particles on mesquite leaves were analyzed in order to characterize the deposited particles and to determine the spatial deposition patterns of various particle types throughout the Phoenix area. Particles deposited on polycarbonate filters were also analyzed for comparison. Silicon-rich, calcium-silicon, sulfates, iron-rich, chlorine-rich, potassium-rich, and metal-rich particle groups emerged. Most of the chlorine- and potassium-rich particles originated from the leaves. The silicon- and iron-rich particles were observed at all sampling sites and were most abundant in the southern part of the sampling domain, where agricultural activities exist. Other sources of silicon-rich particles included construction and traffic. The calcium-silicon particles were also observed at all sampling sites, but they were most abundant at a site in the northwestern part of the region. These particles may have originated from cement or soil. The sulfate particles were less abundant than the silicon-rich and calcium-silicon particles and were not observed at all sampling sites. Local sources of sulfate particles included motor vehicle emissions, and distant sources included coal-burning power plants.