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COMPOSITION OF PM2.5 IN RESEARCH TRIANGLE PARK, NORTH CAROLINA, USA DURING THE WINTER OF 2003
Citation:
Edney, E O., T E. Kleindienst, M Lewandowski, AND M. Jaoui. COMPOSITION OF PM2.5 IN RESEARCH TRIANGLE PARK, NORTH CAROLINA, USA DURING THE WINTER OF 2003. Presented at American Association for Aerosol Research National Meeting, Anaheim, CA, October 20-24, 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:
Ambient PM2.5 contains a variety of inorganic compounds, nearly all of which can be measured, and a complex mixture of organic compounds, of which less than 20% of the constituents have been identified. While many of these compounds are directly emitted into the troposphere, a significant component of PM2.5 comes from gas-to-particle conversion of photooxidation products of biogenic and anthropogenic compounds. Determining the relative contributions of primary emissions versus secondary production is critically needed to develop cost-effective control strategies for reducing ambient PM2.5 concentrations. As a step in addressing this issue we carried out a short-term field study in Research Triangle Park, NC during the summer of 2000 to identify inorganic and organic compounds in PM2.5. The purpose of the present study was to gather similar information for PM2.5 samples collected during the winter. Specifically, a short term field study was undertaken in Research Triangle Park, NC, USA during the winter of 2003 (1) to determine the inorganic composition of PM2.5 and (2) 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 sampling site was in a semi-rural environment with expected impacts from both biogenic and anthropogenic sources. Six PM2.5 samples were collected and analyzed for gravimetric mass, inorganic composition by ion chromatography, carbon by a thermal-optical method, and polar oxygenated compounds by GC-MS after derivatization of the solvent extracts. Detailed analyses of the organic fraction were carried out using the O-(2,3,4,5,6-pentafluorobenzyl)hydroxy amine (PFBHA) method for the derivatization of carbonyl groups, N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA) method for hydroxyl groups, and the PFBHA/BSTFA double derivative method. The ambient PM2.5 mass concentrations for the winter field study ranged between 6 and 13 ug m-3, with average mass concentrations of 1.8 ug m-3 sulfate, 0.5 ug m-3 nitrate, and 2.9 ug m-3 total carbon. GC-MS analyses of the organic extracts were consistent with the presence of compounds containing polar carbonyl and hydroxyl functional groups. These data also revealed significant differences between the nature of the PM2.5 polar organic fractions collected during the summer of 2000 and the winter of 2003. While the winter and summer data were similar as shown by the detection of polar organic tracers for both secondary organic aerosol from biogenics and primary wood smoke emissions, the levoglucosan levels suggested wood smoke emissions were the more important of the two processes during the winter sampling period.
This work has been funded fully, or in part, by the United States Environmental Protection Agency, under Contract Number 68-D00-206 to ManTech Environmental Technology, Inc. It has been subjected to Agency review and approved for publication.