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Polar Organic Oxygenates in PM2.5 at a Southeastern Site in the United States

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Abstract:A field study was undertaken in Research Triangle Park, NC, USA, during the summer of 2000 to identify classes of polar oxygenates in PM2.5 containing carbonyl and/or hydroxyl functional groups and, to the extent possible, determine the individual particle-bound oxygenates that make up each class. The selected site was in a semi-rural environment with expected impacts from both biogenic and anthropogenic sources. PM2.5 samples were collected and analyzed for gravimetric mass, inorganic composition by ion chromatography, polar oxygenated compounds by gas chromatography-mass spectroscopy after derivatization of the solvent extracts, organic and elemental carbon by a thermal-optical method, and chemical functional groups by infrared spectroscopy. The chemical analyses also included determining the polarity of the PM2.5 by measuring the organic carbon concentrations in a series of extraction solvents of increasing polarity. The ambient PM2.5 mass concentrations ranged between 9 and 30 ug m-3, with an average mass composition of 28% sulfate, 6% nitrate, 12% ammonium, 39% organic carbon compound, 2% elemental carbon, and 12% liquid water at a relative humidity of 43%. Organic carbon analyses of the organic extracts indicated approximately 89% of the extractable organic carbon was more polar in nature than that extracted by n-hexane. Infrared analysis of the PM2.5 was consistent with the presence of significant levels of polar carbonyl and hydroxyl functional groups. The polar nature of the organic fraction was further supported by the observation that the inorganic fraction accounted for only about 80% of measured liquid water concentrations in the PM2.5. The mass spectra data were consistent with the presence of the following classes of oxygenates: oxo monocarboxylic acids, trihydroxy monocarboxylic acids, dihydroxy dicarboxylic acids, hydroxy dicarboxylic acids, normal dicarboxylic acids, oxo dicarboxylic acids, methoxy dicarboxylic acids, tricarboxylic acids, triols, and photooxidation products of a-pinene and toluene. In particular, five secondary organic aerosol compounds observed in a smog chamber irradiation of an a-pinene/NOx/air mixture were detected in ambient PM2.5.

The U.S. Environmental Protection Agency through its Office of Research and Development funded and collaborated in the research described here under Contract 68-D-00-206 to ManTech Environmental Technology, Inc. It has been subject to Agency review and approved for publication. Mention of trade names or commercial products does not constitute an endorsement or recommendation for use.
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Citation:Edney, E. O., T. E. Kleindienst, T. S. Conver, C. D. Mciver, and W. Weathers. Polar Organic Oxygenates in PM2.5 at a Southeastern Site in the United States. ATMOSPHERIC ENVIRONMENT 38(28):3947-3965, (2003).
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Contact: Liz Hope - (919) 541-2785 or hope.elizabeth@epa.gov
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Division: Human Exposure & Atmospheric Sciences Division
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Branch: Process Modeling Research Branch
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Product Type: Journal
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Published: 09/01/2003
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Bullet Item Polar Organic Oxygenates in PM2.5 at a Southeastern Site in the United States
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Bullet Item Science Version of PM Chemistry Model
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