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COMPOSITION OF PM 2.5 DURING THE SUMMER OF 2003 IN RESEARCH TRIANGLE PARK, NC
Citation:
LEWANDOWSKI, M., M. JAOUI, T. E. KLEINDIENST, J. H. OFFENBERG, AND E. O. EDNEY. COMPOSITION OF PM 2.5 DURING THE SUMMER OF 2003 IN RESEARCH TRIANGLE PARK, NC. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 41(19):4073-4083, (2007).
Impact/Purpose:
1. Conduct laboratory studies with scientists from Caltech, the University of Antwerp, and the NOAA Aeronomy Laboratory to improve treatments of SOA Chemistry and N2O5 chemistry in CMAQ.
2. Analyze ambient PM2.5 samples in Research Triangle Park, NC, Detroit, MI and Pasadena, CA and when available compare field data with CMAQ predictions obtained from AMD.
3. In 2005 recommend improvements to AMD for the treatment of SOA chemistry in CMAQ.
4. By the end of FY06, deliver an improved SOA chemistry model to AMD who will incorporate the model into CMAQ.
5. By the end of 2007, deliver an improved N2O5 chemistry model to AMD who will incorporate the model into CMAQ.
Description:
A field study was carried out during the summer of 2003 to examine the overall composition of fine particulate matter (PM2.5) in Research Triangle Park, North Carolina, USA, with particular emphasis on polar compounds from secondary organic aerosol (SOA). Collected samples were examined for gravimetric mass, organic and elemental carbon concentrations, inorganic ion concentrations, and detailed organic composition. On average, the ambient PM2.5 was found to consist of 41% organic matter, 2% elemental carbon, 12% ammonium, 37% sulfate, and less than 1% nitrate and oxalate. Mass concentrations ranged from 6.4 to 31.4 µg m-3. The acidity of the aerosol was also estimated, and higher PM2.5 and organic mass concentrations were generally observed under acidic conditions. A suite of chemical derivatization methods was used in conjunction with gas chromatography-mass spectrometry (GC-MS) to identify and quantify 29 polar organic compounds. Most of these compounds have been previously identified in laboratory photooxidation studies from hydrocarbon precursors, including isoprene, monoterpenes, ß-caryophyllene, and toluene. From laboratory studies, several of these polar compounds have been proposed as tracers for SOA, and concentrations measured in this study indicate the contributions of the precursor hydrocarbons to ambient SOA could be important. Some of the organic tracers, particularly those associated with isoprene SOA, represented a greater fraction of the organic carbon when the aerosol was acidic.