Individual particle types in the aerosol of Phoenix, Arizona

"Zero-count' particles, consisting entirely of elements lighter than Na, dominated the fine fraction (≤2μm). 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. -from Authors