Functional group characterization of indoor, outdoor, and personal PM2.5: results from RIOPA

Fourier transform infrared (FTIR) spectra of outdoor, indoor, and personal fine particulate matter (PM 2 . 5 ) samples were collected during the Relationship of Indoor, Outdoor, and Personal Air (RIOPA) study. FTIR spectroscopy provides functional group information about the entire PM 2 . 5 sample without any chemical preparation. It is particularly important to characterizing the poorly understood organic fraction of PM 2 . 5 . To our knowledge this is the first time that FTIR spectroscopy has been applied to a PM 2 . 5 exposure study. The results were used to chemically characterize indoor air and personal exposure. Sulfate was strongest in outdoor samples, which is consistent with the generally accepted understanding that sulfate is of outdoor origin. Absorbances attributed to soil dust were also seen in many outdoor and some indoor and personal samples. Inorganic nitrate absorbances were a common feature of many California and some New Jersey samples. Carbonyl absorbances showed substantial variation in strength, number of peaks, and wave number shift between samples, indicating variability in composition and sources. Absorbances attributed to aliphatic hydrocarbon and amide functional groups were enhanced in many personal and indoor samples, which suggested the influence of indoor sources in these homes. We speculate that meat cooking is one possible source of particulate amides.