Characterization of Individual Particles in the Phoenix Urban Aerosol Using Electron-Beam Instruments

More than 8000 individual particles from the Phoenix aerosol were analyzed by using an analytical scanning electron microscope. The compositions of the aerosol were similar at the three sampling locations. Approximately 75% of the coarse particle fraction (>1 pm) is crustal material, i.e., clays, quartz, feldspars, calcite, etc. The remaining coarse particles consist mainly of biological material, S compounds, Pb salts from automobiles, and other anthropogenic particles. S-bearing particles comprise an estimated 60-80% of the submicron aerosol fraction. Presumably, the most abundant S species is (NH₄)₂SO₄; however, many of the S-bearing particles contain various amounts of other elements such as Zn, Pb, Cu, Na, Ca, As, and K. The remainder of the submicron fraction is composed largely of automobile Pb halides and particles from a variety of anthropogenic sources. Some of the anthropogenic particles have been pinpointed to specific sources, but in most cases to date only possible sources are suggested.