Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 9 17 2009 10.5194/acp-9-6633-2009 http://www.atmos-chem-phys.net/9/6633/2009/ http://www.atmos-chem-phys.net/9/6633/2009/acp-9-6633-2009.html http://www.atmos-chem-phys.net/9/6633/2009/acp-9-6633-2009.pdf 6633 6653 2009-09-11 Mexico City aerosol analysis during MILAGRO using high resolution aerosol mass spectrometry at the urban supersite (T0) – Part 1: Fine particle composition and organic source apportionment A. C. Aiken D. Salcedo M. J. Cubison J. A. Huffman P. F. DeCarlo I. M. Ulbrich K. S. Docherty D. Sueper J. R. Kimmel D. R. Worsnop A. Trimborn M. Northway E. A. Stone J. J. Schauer R. M. Volkamer E. Fortner B. de Foy J. Wang A. Laskin V. Shutthanandan J. Zheng R. Zhang J. Gaffney N. A. Marley G. Paredes-Miranda W. P. Arnott L. T. Molina G. Sosa J. L. Jimenez jose.jimenez@colorado.edu Department of Chemistry, University of Colorado at Boulder, 215 UCB, Boulder, CO 80309, USA Cooperative Institute for Research in the Environmental Sciences (CIRES), University of Colorado at Boulder, 216 UCB, Boulder, CO 80309, USA Centro de Investigaciones Quimicas, Universidad Autónoma del Estado de Morelos, Cuernavaca Morelos, Mexico Department of Atmospheric and Oceanic Sciences, University of Colorado at Boulder, UCB 311, Boulder, CO 80309, USA Aerodyne Research Inc., 45 Manning Rd., Billerica, MA, 01821, USA Environmental Chemistry and Technology Program, University of Wisconsin-Madison, 660 North Park St., Madison, WI 53706, USA Montana State University, Bozeman, MT 59717, USA Texas A&M, 3150 TAMU, College Station, TX 77843, USA Saint Louis University, St. Louis, MO 63108, USA Brookhaven National Laboratory, P.O. Box 5000, Upton, NY 11973, USA Pacific Northwest National Laboratory, Richland, WA, USA University of Arkansas, 2801 S. University Avenue, Little Rock, AR 72204, USA University of Nevada Reno and the Desert Research Institute, Reno, NV, USA Molina Center for Energy and the Environment and Massachusetts Institute of Technology, USA IMP, Eje Central Norte Lazaro Cardenas 152, Mexico City, DF 07730, Mexico now at: Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology Zurich (ETH-Zurich), 8092 Zurich, Switzerland now at: Paul Scherrer Institut, 5232 Villigen-PSI, Switzerland now at: Department of Meteorology, University of Reading, Reading, UK Submicron aerosol was analyzed during the MILAGRO field campaign in March 2006 at the T0 urban supersite in Mexico City with a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and complementary instrumentation. Mass concentrations, diurnal cycles, and size distributions of inorganic and organic species are similar to results from the CENICA supersite in April 2003 with organic aerosol (OA) comprising about half of the fine PM mass. Positive Matrix Factorization (PMF) analysis of the high resolution OA spectra identified three major components: chemically-reduced urban primary emissions (hydrocarbon-like OA, HOA), oxygenated OA (OOA, mostly secondary OA or SOA), and biomass burning OA (BBOA) that correlates with levoglucosan and acetonitrile. BBOA includes several very large plumes from regional fires and likely also some refuse burning. A fourth OA component is a small local nitrogen-containing reduced OA component (LOA) which accounts for 9% of the OA mass but one third of the organic nitrogen, likely as amines. OOA accounts for almost half of the OA on average, consistent with previous observations. OA apportionment results from PMF-AMS are compared to the PM_2.5 chemical mass balance of organic molecular markers (CMB-OMM, from GC/MS analysis of filters). Results from both methods are overall consistent. Both assign the major components of OA to primary urban, biomass burning/woodsmoke, and secondary sources at similar magnitudes. The 2006 Mexico City emissions inventory underestimates the urban primary PM_2.5 emissions by a factor of ~4, and it is ~16 times lower than afternoon concentrations when secondary species are included. Additionally, the forest fire contribution is at least an order-of-magnitude larger than in the inventory. Aiken, A. C., de Foy, B., Wiedinmyer, C., et al.: Mexico City aerosol analysis during MILAGRO using high resolution aerosol mass spectrometry at the urban supersite (T0) – Part 2: Analysis of the biomass burning contribution and the modern carbon fraction, Atmos. Chem. Phys., in preparation, 2009. Aiken, A. C., DeCarlo, P. F. and Jimenez, J. 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