INDIVIDUAL PARTICLE TYPES IN THE AEROSOL OF PHOENIX, ARIZONA

Aerosol samples were collected in Phoenix, AZ, from July 1989 through April 1990. Elemental compositions were determined for individual particles using an electron microprobe with an energy-dispersive X-ray spectrometer. Multivariate statistical techniques were used to identify particle types. ''Zero-count'' particles, consisting entirely of elements lighter than Na, dominate the fine fraction (less than or equal to 2 mu m). Si- and Ca-rich mineral particles dominate the coarse fraction but are also abundant in the fine fraction. S-bearing particles are common in the fine fraction as well. Lower Pb concentrations in the 1989-1990 samples relative to samples collected in the early 1980s probably reflect decreased usage of leaded gasoline. A difference in the number of S-bearing particles was also noted. S-bearing particles comprised 30% of the fine fraction reported for samples collected in the early 1980s and 17% of the fine fraction in the 1989-1990 samples.