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PM2.5 ORGANIC COMPOSITION FROM SEVERAL SITES IN THE UNITED STATES
Citation:
Edney, E O., R. E. Speerand, W S. Weathers, T. E. Kleindienst, E. W. Corse, AND C. D. McIver. PM2.5 ORGANIC COMPOSITION FROM SEVERAL SITES IN THE UNITED STATES. Presented at American Association for Aerosol Research, Charlotte, Nc, October 7-11, 2002.
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:
Organic constituents make up an important component of fine particulate matter (PM2.5) in ambient environments. While part of the composition of organic aerosol results from emissions of primary sources, an additional component appears to come from gas-to-particle conversion of photooxidation products of natural and anthropogenic hydrocarbons. These secondary products have been measured in simulated atmospheres in this and other laboratories. However, except under specialized circumstances, many of the oxidation products of anthropogenic origin are rarely reported in the fine particle fraction of ambient aerosols.
A study was conducted to examine the summertime composition of PM2.5 at four locations along the Mid-Atlantic portion of the United States: a semi-rural field site in Research Triangle Park, North Carolina and urban sites in Baltimore, Maryland, Philadelphia, Pennsylvania, and New York, New York. Measurements were made for the inorganic and organic constituents of the fine particulate mass. Detailed analysis of the organic carbon was also undertaken using a double derivatization technique with PFBHA for the derivatization of carbonyl groups and BSTFA for hydroxyl groups. Inorganic ion (sulfate and nitrate) measurements, liquid water, and gravimetric measurements were also made from an aerosol collections on Teflon filters. Organic and elemental carbon were measured using a thermo-optical technique from aerosol collections onto quartz filters.
The study was carried out over a three week period from 10 July - 02 August 2001. Samples for seven 24-hour and four 48-hour sampling periods were taken. Gravimetric results indicated that total mass loadings ranged from 5.7 to 42 ?g m-3 for the sampling periods during that time frame. At the rural site, the organic mass was estimated to comprise 57% of the total gravimetric mass. By contrast, at the urban site on average, the organic mass was estimated to comprise 32% of the total mass. The detailed analysis of the organic fraction from each of the urban sites showed chemical markers related to photooxidation products of aromatic hydrocarbons; oxygenated products from the rural site indicated the presence of biogenic precursors. In general, the aerosol was highly oxygenated and a wide range of substituted diacids appeared to be some of the dominant compounds found by this analysis approach.
This work has been funded fully, or in part, by the United States Environmental Protection Agency, under Contract Number 68-D5-0049 to ManTech Environmental Technology, Inc. It has been subjected to Agency review and approved for publication.