Microscopical analysis of aerosols transported from St. Louis

The study, sponsored by the Environmental Protection Agency, was to measure the transport and fate of sulfur dioxide from St. Louis' urban and powerplant plumes. These plumes were traced and sampled by instrumented aircraft at distances up to 300 miles from St. Louis. In addition to sampling SO/sub 2/, a special 4 stage impactor was constructed for sampling aerosols for microscopical analysis. Samples were returned to St. Louis within 2-4h after collecting and identified or classified by morphological properties. The major components were sulfuric acid or ammonium sulfate, usually found on the third stage (0.5 ..mu..m) and often 5 ..mu..m in length, indicating crystallization. Fly ash and mineral particles, some unusually carbonaceous deposits, and submicrometer sized clays and other minerals were also found. This study provided the first direct verification of sulfuric acid in urban atmosphere and also proof of the long range transport.