Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 9 1 2009 10.5194/acpd-9-4805-2009 http://www.atmos-chem-phys-discuss.net/9/4805/2009/ http://www.atmos-chem-phys-discuss.net/9/4805/2009/acpd-9-4805-2009.html http://www.atmos-chem-phys-discuss.net/9/4805/2009/acpd-9-4805-2009.pdf 4805 4871 2009-02-24 Evaluating simulated primary anthropogenic and biomass burning organic aerosols during MILAGRO: implications for assessing treatments of secondary organic aerosols J. D. Fast A. C. Aiken J. Allan L. Alexander T. Campos M. R. Canagaratna E. Chapman P. F. DeCarlo B. de Foy J. Gaffney J. de Gouw J. C. Doran L. Emmons A. Hodzic S. C. Herndon G. Huey J. T. Jayne J. L. Jimenez L. Kleinman W. Kuster N. Marley L. Russell C. Ochoa T. B. Onasch M. Pekour C. Song I. M. Ulbrich C. Warneke D. Welsh-Bon C. Wiedinmyer D. R. Worsnop X.-Y. Yu R. Zaveri Pacific Northwest National Laboratory, Richland, Washington, USA University of Colorado, Boulder Colorado, USA University of Manchester, Manchester, UK National Center for Atmospheric Research, Boulder, Colorado, USA Aerodyne Research Inc., Billerica, Massachusetts, USA Paul Scherrer Institut, Switzerland Saint Louis University, Saint Louis, Missouri, USA University of Arkansas – Little Rock, Little Rock, Arkansas, USA NOAA Earth System Research Laboratory & Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA Georgia Institute of Technology, Atlanta, Georgia, USA Brookhaven National Laboratory, Upton, New York, USA University of California – San Diego, San Diego, California, USA Universidad Nacional Aut ´onoma de M´exico, Mexico City, Mexico Simulated primary organic aerosols (POA), as well as other particulates and trace gases, in the vicinity of Mexico City are evaluated using measurements collected during the 2006 Megacity Initiative: Local and Global Research Observations (MILAGRO) field campaigns. Since the emission inventories and dilution will directly affect predictions of total organic matter and consequently total particulate matter, our objective is to assess the uncertainties in predicted POA before testing and evaluating the performance of secondary organic aerosol (SOA) treatments. Carbon monoxide (CO) is well simulated on most days both over the city and downwind, indicating that transport and mixing processes were usually consistent with the meteorological conditions observed during MILAGRO. Predicted and observed elemental carbon (EC) in the city was similar, but larger errors occurred at remote locations since the overall CO/EC emission ratios in the national emission inventory were lower than in the metropolitan emission inventory. Components of organic aerosols derived from Positive Matrix Factorization of data from several Aerodyne Aerosol Mass Spectrometer instruments deployed both at ground sites and on research aircraft are used to evaluate the model. 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