Secondary Formation and the Smoky Mountain Organic Aerosol:  An Examination of Aerosol Polarity and Functional Group Composition During SEAVS

Size-resolved particle samples were collected in the Smoky Mountains at Look Rock, TN, during the Southeastern Aerosol and Visibility Study (SEAVS) July−August 1995 and analyzed directly by Fourier transform infrared (FTIR) spectroscopy for functional group and chemical bond information. Twenty-eight samples were also gently rinsed in hexane, acetone, and water and reanalyzed after each rinse. Direct FTIR analyses of substrates rinsed with solvents enabled separation by polarity and identification of sulfur-containing organics even though samples were too small for traditional extraction and analysis (approximately 10−15 μg). The submicron organic aerosol was predominantly polar. Most of the nonpolar material, including aliphatic carbon and various minerals, was concentrated in particles greater than 1.0 μm and is most likely from primary biogenic and geogenic emissions, such as plant waxes and windblown soil dust. Unlike Los Angeles, carbonyl size distributions were unimodal and usually peaked in the 0.5−1.0 μm diameter size range. The predominance of sulfate, carbonyl, and organosulfur absorbances, the polarity of the aerosol, and the carbonyl size distributions indicate that secondary formation processes have a large influence on the concentrations, composition, and size distributions of the Smoky Mountain aerosol.