Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 7 6 2007 10.5194/acpd-7-17825-2007 http://www.atmos-chem-phys-discuss.net/7/17825/2007/ http://www.atmos-chem-phys-discuss.net/7/17825/2007/acpd-7-17825-2007.html http://www.atmos-chem-phys-discuss.net/7/17825/2007/acpd-7-17825-2007.pdf 17825 17871 2007-12-13 Total Observed Organic Carbon (TOOC): A synthesis of North American observations C. L. Heald heald@atmos.berkeley.edu A. H. Goldstein J. D. Allan A. C. Aiken E. Apel E. L. Atlas A. K. Baker T. S. Bates A. J. Beyersdorf D. R. Blake T. Campos H. Coe J. D. Crounse P. F. DeCarlo J. A. de Gouw E. J. Dunlea F. M. Flocke A. Fried P. Goldan R. J. Griffin S. C. Herndon J. S. Holloway R. Holzinger J. L. Jimenez W. Junkermann W. C. Kuster A. C. Lewis S. Meinardi D. B. Millet T. Onasch A. Polidori P. K. Quinn D. D. Riemer J. M. Roberts D. Salcedo B. Sive A. L. Swanson R. Talbot C. Warneke R. J. Weber P. Weibring P. O. Wennberg A. E. Wittig R. Zhang J. Zheng W. Zheng Department of Environmental Science and Policy Management, University of California, Berkeley, CA, USA School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK Department of Atmospheric and Oceanic Science, University of Colorado, Boulder, CO, USA Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, CO, USA RSMAS, Division of Marine and Atmospheric Chemistry, University of Miami, Miami, FL, USA Department of Chemistry, University of California, Irvine, CA, USA NOAA/PMEL, Seattle, WA, USA California Institute of Technology, Pasadena, CA, USA Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado at Boulder, Boulder, CO, USA Chemical Sciences Division, NOAA Earth System Research Laboratory, Boulder CO, USA Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH Aerodyne Research, Inc., Billerica, MA, USA Institute for Marine and Atmospheric Research (IMAU), Utrecht University, Utrecht, The Netherlands Forschungszentrum Karlsruhe, IMK-IFU, Garmisch-Partenkirchen, Germany Department of Chemistry, University of York, Heslington, York, UK Department of Soil, Water and Climate, University of Minnesota, St. Paul, MN, USA Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA, USA Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Av. Cuernavaca, Mexico Northrop Grumman Space Technology, Chemistry Technology Department, Redondo Beach, CA, USA School of Earth and Atmospheric Sciences , Georgia Institute of Technology, Atlanta, GA, USA Department of Civil Engineering, City College of New York, New York, NY, USA Department of Atmospheric Sciences, Texas A and M University, College Station, TX, USA Measurements of organic carbon compounds in both the gas and particle phases measured upwind, over and downwind of North America are synthesized to examine the total observed organic carbon (TOOC) over this region. These include measurements made aboard the NOAA WP-3 and BAe-146 aircraft, the NOAA research vessel Ronald H. Brown, and at the Thompson Farm and Chebogue Point surface sites during the summer 2004 ICARTT campaign. Both winter and summer 2002 measurements during the Pittsburgh Air Quality Study are also included. Lastly, the spring 2002 observations at Trinidad Head, CA, surface measurements made in March 2006 in Mexico City and coincidentally aboard the C-130 aircraft during the MILAGRO campaign and later during the IMPEX campaign off the northwestern United States are incorporated. Concentrations of TOOC in these datasets span more than two orders of magnitude. The daytime mean TOOC ranges from 4.0 to 456 μgC m<sup>−3</sup> from the cleanest site (Trinidad Head) to the most polluted (Mexico City). Organic aerosol makes up 3–17% of this mean TOOC, with highest fractions reported over the northeastern United States, where organic aerosol can comprise up to 50% of TOOC. Carbon monoxide concentrations explain 46 to 86% of the variability in TOOC, with highest TOOC/CO slopes in regions with fresh anthropogenic influence, where we also expect the highest degree of mass closure for TOOC. 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