FTIR analysis of Smoky Mountain aerosol

As part of the Southeastern Aerosol and Visibility Study in the Smoky Mountains (July 15-August 25, 1995), we collected samples on ZnSe discs in a Hering Low Pressure Impactor (LPI) from 7am-7pm daily. Impactor size cuts were 2.0, 1.0, 0.50, 0.26, 0.12, 0.05 um. Samples, blanks, and polystyrene standards were analyzed in a Mattson Research Series 100 FTIR Spectroscope. After initial, non-destructive analysis, a subset of samples were gently rinsed with hexane, acetone, and water in succession and analyzed by FTIR after each rinse. Sulfate and carbonyl were consistently observed in sub-micron particles, and commonly detected with soil dust in the 1-2 um size fraction. Carbonyl is associated with secondary organic aerosol formation. Aliphatics in the Smoky Mountain aerosol were most prevalent in the 1-2 um size fraction, suggesting a primary biogenic origin (e.g., plant waxes and organic acids). This contrasts with aliphatic size distributions in Los Angeles aerosols, which peaked below 0.12 um, and were attributed to automotive emissions.