You are here:
POLAR ORGANIC OXYGENATES IN PM2.5 AT A SOUTHEASTERN SITE IN THE UNITED STATES
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).
Impact/Purpose:
1. Using laboratory and field study data generated during FY99-FY04, develop a science version of a PM chemistry model for predicting ambient concentrations of water, inorganics, and organics in PM2.5 samples. The model will include the Aerosol Inorganic Model for predicting concentrations of inorganic compounds and a computational chemistry-based method for predicting concentrations of organic compounds.
2. Identify and evaluate methods for analyzing the polar fraction of PM2.5 samples.
3. Carry out short term field studies in Research Triangle Park, North Carolina in the summer and the winter to determine the composition of the organic fraction of ambient PM2.5 samples, with special emphasis placed on identifying and determining ambient concentrations of polar compounds.
4. Conduct laboratory studies to establish the chemical composition of secondary organic aerosol (SOA) and to determine source signatures for aromatic and biogenic SOA.
5. Conduct laboratory and theoretical investigations of thermodynamic properties of polar organic compounds.
6. Evaluate the science version of the PM chemistry model using laboratory and field data generated under this task as well as other available data in the literature.
7. Conduct PM chemistry-related special studies for OAQPS
Description:
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.