A24C-01 INVITED 

Polluted Marine Boundary Layer Measurement of Nitryl Chloride; a Product of Nightime NOx and Aerosol Chemistry

* Roberts, J M (James.M.Roberts@noaa.gov), Chemical Sciences Division, NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305, United States Osthoff, H D (hostoff@ucalgary.ca), Department of Chemistry University of Calgary, 2500 University Drive NW, Calgary, ALB T2N 1N4, Canada Brown, S S (Steven.S.Brown@noaa.gov), Chemical Sciences Division, NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305, United States Ravishankara, A R (A.R.Ravishankara@noaa.gov), Chemical Sciences Division, NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305, United States Ravishankara, A R (A.R.Ravishankara@noaa.gov), Cooperative Institute for Research in the Environmental Sciences, University of Colorado, CB 216, Boulder, CO 80309, United States Williams, E J (Eric.J.Williams@noaa.gov), Chemical Sciences Division, NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305, United States Williams, E J (Eric.J.Williams@noaa.gov), Cooperative Institute for Research in the Environmental Sciences, University of Colorado, CB 216, Boulder, CO 80309, United States Lerner, B M (Brian.Lerner@noaa.gov), Chemical Sciences Division, NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305, United States Lerner, B M (Brian.Lerner@noaa.gov), Cooperative Institute for Research in the Environmental Sciences, University of Colorado, CB 216, Boulder, CO 80309, United States Talukdar, R K (Ranajit.K.Talukdar@noaa.gov), Chemical Sciences Division, NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305, United States Talukdar, R K (Ranajit.K.Talukdar@noaa.gov), Cooperative Institute for Research in the Environmental Sciences, University of Colorado, CB 216, Boulder, CO 80309, United States Burkholder, J B (James.B.Burkholder@noaa.gov), Chemical Sciences Division, NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305, United States Burkholder, J B (James.B.Burkholder@noaa.gov), Cooperative Institute for Research in the Environmental Sciences, University of Colorado, CB 216, Boulder, CO 80309, United States Stark, H (Harald.Stark@noaa.gov), Chemical Sciences Division, NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305, United States Stark, H (Harald.Stark@noaa.gov), Cooperative Institute for Research in the Environmental Sciences, University of Colorado, CB 216, Boulder, CO 80309, United States Sommariva, R (Roberto.Sommariva@noaa.gov), Chemical Sciences Division, NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305, United States Sommariva, R (Roberto.Sommariva@noaa.gov), Cooperative Institute for Research in the Environmental Sciences, University of Colorado, CB 216, Boulder, CO 80309, United States Quinn, P K (Patricia.K.Quinn@noaa.gov), Atmospheric Chemistry Program, Pacific Marine Laboratory, NOAA, 7600 Sand Point Way, Seattle, WA 98115, United States Bates, T S (Tim.Bates@noaa.gov), Atmospheric Chemistry Program, Pacific Marine Laboratory, NOAA, 7600 Sand Point Way, Seattle, WA 98115, United States Coffman, D (Derek.Coffman@noaa.gov), Atmospheric Chemistry Program, Pacific Marine Laboratory, NOAA, 7600 Sand Point Way, Seattle, WA 98115, United States Meagher, J F (James.F.Meagher@noaa.gov), Chemical Sciences Division, NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305, United States Fehsenfeld, F C (Fred.C.Fehsenfeld@noaa.gov), Chemical Sciences Division, NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305, United States Fehsenfeld, F C (Fred.C.Fehsenfeld@noaa.gov), Cooperative Institute for Research in the Environmental Sciences, University of Colorado, CB 216, Boulder, CO 80309, United States

The first ambient measurements of nitryl chloride (ClNO₂) were made by I^- chemical ionization mass spectrometry (CIMS) during the TexAQS/GoMACCS 2006 study aboard the NOAA R/V Ronald H Brown. ClNO₂ was associated with the nighttime reaction of N₂O₅ with chloride-containing aerosol particles and was found at mixing ratios as high as 1.2 ppbv (1 minute average) in the Houston-Galveston Bay area. Several instances were observed in which ClNO₂ persisted into the morning hours, resulting in a significant chlorine atom source. Details of the ClNO₂ measurement, features of the ClNO₂ data, and the impact that this active chlorine species can have on morning photochemistry will be discussed.

A24C-02 

Nighttime nitrogen oxide chemistry in the marine boundary layer on board the NOAA research vessel Ronald H. Brown during TexAQS/GoMACCS 2006

* Osthoff, H D (hosthoff@ucalgary.ca), University of Calgary, Department of Chemistry 2500 University Drive NW, Calgary, AB T2N1N4, Canada * Osthoff, H D (hosthoff@ucalgary.ca), NOAA ESRL CSD2, 325 Broadway, Boulder, CO 80305, United States * Osthoff, H D (hosthoff@ucalgary.ca), CIRES, 216 UCB University of Colorado, Boulder, CO 80309, United States Roberts, J M (james.m.roberts@noaa.gov), NOAA ESRL CSD2, 325 Broadway, Boulder, CO 80305, United States Bates, T S (Tim.Bates@noaa.gov), NOAA PMEL, 7600 Sand Point Way NE, Seattle, WA 98115, United States Coffman, D (Derek.Coffman@noaa.gov), NOAA PMEL, 7600 Sand Point Way NE, Seattle, WA 98115, United States Quinn, P K (Patricia.K.Quinn@noaa.gov), NOAA PMEL, 7600 Sand Point Way NE, Seattle, WA 98115, United States Williams, E J (eric.j.williams@noaa.gov), NOAA ESRL CSD2, 325 Broadway, Boulder, CO 80305, United States Williams, E J (eric.j.williams@noaa.gov), CIRES, 216 UCB University of Colorado, Boulder, CO 80309, United States Lerner, B M (brian.lerner@noaa.gov), NOAA ESRL CSD2, 325 Broadway, Boulder, CO 80305, United States Lerner, B M (brian.lerner@noaa.gov), CIRES, 216 UCB University of Colorado, Boulder, CO 80309, United States Stark, H (harald.stark@noaa.gov), NOAA ESRL CSD2, 325 Broadway, Boulder, CO 80305, United States Stark, H (harald.stark@noaa.gov), CIRES, 216 UCB University of Colorado, Boulder, CO 80309, United States Sommariva, R (roberto.sommariva@noaa.gov), NOAA ESRL CSD2, 325 Broadway, Boulder, CO 80305, United States Sommariva, R (roberto.sommariva@noaa.gov), CIRES, 216 UCB University of Colorado, Boulder, CO 80309, United States Kuster, W C (william.c.kuster@noaa.gov), NOAA ESRL CSD2, 325 Broadway, Boulder, CO 80305, United States Gilman, J (jessica.gilman@noaa.gov), NOAA ESRL CSD2, 325 Broadway, Boulder, CO 80305, United States Gilman, J (jessica.gilman@noaa.gov), CIRES, 216 UCB University of Colorado, Boulder, CO 80309, United States Ravishankara, A R (a.r.ravishankara@noaa.gov), NOAA ESRL CSD2, 325 Broadway, Boulder, CO 80305, United States Ravishankara, A R (a.r.ravishankara@noaa.gov), University of Colorado, Department of Chemistry and Biochemistry, Boulder, CO 80309, United States Brown, S S (steven.s.brown@noaa.gov), NOAA ESRL CSD2, 325 Broadway, Boulder, CO 80305, United States

The nitrate radical, NO₃, formed from reaction of NO₂ with O₃, and dinitrogen pentoxide, N₂O₅, formed from subsequent reaction of NO₃ with NO₂, drive several important nocturnal chemical processes, including oxidation of VOCs (by NO₃) and removal of NO_x (= NO + NO₂) by the heterogeneous reaction of N₂O₅ to form either nitric acid, HNO₃, and/or aerosol nitrate. Laboratory studies have shown that uptake of N₂O₅ on sea salt and chloride containing aerosol produces nitryl chloride, ClNO₂, which after sunrise may provide a source of Cl atoms, an important oxidant of VOCs in the marine boundary layer. We have measured NO₃ and N₂O₅, by cavity ring-down spectroscopy, on board the NOAA research vessel Ronald H. Brown during the Texas Air Quality Study - Gulf of Mexico Atmospheric Composition and Climate Study (TexAQS/GoMACCS) 2006. In this presentation, a few aspects of nighttime nitrogen oxide chemistry in the subtropical marine boundary layer are highlighted, including (1) NO₃ and N₂O₅ production and loss rates including uptake on aerosol in order to estimate nighttime HNO₃ production and NO_x loss, and (2) the impact of NO₃ and N₂O₅ heterogeneous uptake to produce labile halogen containing compounds at night.

A24C-03 

Chemical Processing and Transport of Boundary Layer Aerosols During TexAQS/GoMACCS 2006

* Bates, T S (tim.bates@noaa.gov), NOAA/PMEL, 7600 Sand Point Way NE, Seattle, WA 98115, United States * Bates, T S (tim.bates@noaa.gov), JISAO, University of Washington, Seattle, WA 98195, United States Quinn, P K (patricia.k.quinn@noaa.gov), NOAA/PMEL, 7600 Sand Point Way NE, Seattle, WA 98115, United States Quinn, P K (patricia.k.quinn@noaa.gov), JISAO, University of Washington, Seattle, WA 98195, United States Coffman, D J (derek.coffman@noaa.gov), NOAA/PMEL, 7600 Sand Point Way NE, Seattle, WA 98115, United States Schulz, K (kristen.schulz@noaa.gov), NOAA/PMEL, 7600 Sand Point Way NE, Seattle, WA 98115, United States Johnson, J E (james.e.johnson@noaa.gov), JISAO, University of Washington, Seattle, WA 98195, United States Covert, D S (dcovert@u.washington.edu), JISAO, University of Washington, Seattle, WA 98195, United States

The air quality and climate forcing impacts of atmospheric aerosols in a metropolitan region depend on the amount, composition, and size of the aerosol transported into the region, the input of aerosols and aerosol precursors within the region, and the subsequent chemical processing in the atmosphere. These factors were studied in the Houston-Galveston-Gulf of Mexico region, aboard the NOAA R/V Ronald H. Brown during the Texas Air Quality Study and Gulf of Mexico Atmospheric Composition and Climate Study (TexAQS/GoMACCS 2006). The aerosol measured in the Gulf of Mexico during onshore flow (low radon concentrations indicating no contact with land for several days) was highly impacted by Saharan dust and what appear to be ship emissions (acidic sulfate and nitrate). Mean (median) mass concentrations of the total submicrometer and supermicrometer aerosol were 6.5 (4.6) µg m-3 and 17.2 (8.7) µg m-3, respectively. These mass loadings of "background" aerosol are much higher than typically observed in the marine atmosphere and thus have a substantial impact on particulate matter (PM) loadings in the Houston-Galveston area. As this background aerosol moved onshore, local urban and industrial sources added an organic rich submicrometer component (66% particulate organic matter (POM), 20% sulfate, 14% elemental carbon) resulting in mean (median) mass concentrations of the total submicrometer and supermicrometer aerosol of 10.0 (9.1) µg m-3 and 16.8 (11.2) µg m-3, respectively. These airmasses, with minimal processing of urban emissions contained the highest SO2/(SO2 + SO4) ratios and the highest hydrocarbon-like organic aerosol to total organic aerosol ratios (HOA/POM). In contrast, during periods of offshore flow, the aerosol was more processed and, therefore, much richer in oxidized organic aerosol (OOA). Mean (median) mass concentrations of the total submicrometer and supermicrometer aerosol were 20.8 (18.6) µg m-3 and 7.4 (5.0) µg m-3, respectively. Sorting airmasses based on their trajectories and time-over-land provides a means to examine the effects of transport and subsequent chemical processing. Understanding and parameterizing these processes is critical for the chemical transport modeling that forms the basis for air quality forecasts and radiative forcing calculations. http://saga.pmel.noaa.gov/data/

A24C-04 

Chemical Transformation and Optical Properties of Aerosols From Urban Areas During the TexAQS/GoMACCS Study

* Middlebrook, A M (Ann.M.Middlebrook@noaa.gov), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States Bahreini, R (Roya.Bahreini@noaa.gov), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States Bahreini, R (Roya.Bahreini@noaa.gov), University of Colorado CIRES, PO Box 0216, Boulder, CO 80309, United States Dunlea, E J (Edward.Dunlea@colorado.edu), University of Colorado CIRES, PO Box 0216, Boulder, CO 80309, United States DeCarlo, P D (Peter.DeCarlo@colorado.edu), University of Colorado Dept of Chemistry, PO Box 0215, Boulder, CO 80309, United States Jimenez, J L (Jose.Jimenez@colorado.edu), University of Colorado CIRES, PO Box 0216, Boulder, CO 80309, United States Jimenez, J L (Jose.Jimenez@colorado.edu), University of Colorado Dept of Chemistry, PO Box 0215, Boulder, CO 80309, United States Baynard, T (Tahllee.Baynard@comcast.net), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States Baynard, T (Tahllee.Baynard@comcast.net), University of Colorado CIRES, PO Box 0216, Boulder, CO 80309, United States Spackman, J R (Ryan.Spackman@noaa.gov), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States Spackman, J R (Ryan.Spackman@noaa.gov), University of Colorado CIRES, PO Box 0216, Boulder, CO 80309, United States Schwarz, J P (Joshua.P.Schwarz@noaa.gov), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States Schwarz, J P (Joshua.P.Schwarz@noaa.gov), University of Colorado CIRES, PO Box 0216, Boulder, CO 80309, United States Watts, L A (Laurel.A.Watts@noaa.gov), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States Watts, L A (Laurel.A.Watts@noaa.gov), University of Colorado CIRES, PO Box 0216, Boulder, CO 80309, United States Thomson, D S (David.S.Thomson@noaa.gov), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States Thomson, D S (David.S.Thomson@noaa.gov), University of Colorado CIRES, PO Box 0216, Boulder, CO 80309, United States Wollny, A G (Adam.Wollny@noaa.gov), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States Wollny, A G (Adam.Wollny@noaa.gov), University of Colorado CIRES, PO Box 0216, Boulder, CO 80309, United States Gallar, C (Carlos.Gallar@noaa.gov), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States Gallar, C (Carlos.Gallar@noaa.gov), University of Colorado CIRES, PO Box 0216, Boulder, CO 80309, United States Brock, C A (Charles.A.Brock@noaa.gov), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States Holloway, J S (John.S.Holloway@noaa.gov), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States Holloway, J S (John.S.Holloway@noaa.gov), University of Colorado CIRES, PO Box 0216, Boulder, CO 80309, United States de Gouw, J A (Joost.deGouw@noaa.gov), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States de Gouw, J A (Joost.deGouw@noaa.gov), University of Colorado CIRES, PO Box 0216, Boulder, CO 80309, United States Warneke, C (Carsten.Warneke@noaa.gov), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States Warneke, C (Carsten.Warneke@noaa.gov), University of Colorado CIRES, PO Box 0216, Boulder, CO 80309, United States Ryerson, T B (Thomas.B.Ryerson@noaa.gov), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States Trainer, M (Michael.Trainer@noaa.gov), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States Fehsenfeld, F C (Fred.C.Fehsenfeld@noaa.gov), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States Fehsenfeld, F C (Fred.C.Fehsenfeld@noaa.gov), University of Colorado CIRES, PO Box 0216, Boulder, CO 80309, United States Meagher, J F (James.F.Meagher@noaa.gov), NOAA ESRL, 325 Broadway, Boulder, CO 80305, United States

Size-resolved, non-refractory (NR) aerosol composition was measured on a 10-second basis and with high sensitivity aboard the NOAA WP-3D aircraft using an Aerodyne Compact Time-of-Flight Aerosol Mass Spectrometer (C-ToF AMS) during the 2006 Texas Air Quality Study/Gulf of Mexico Atmospheric Composition and Climate Study (TexAQS/GoMACCs). Fine features in the C-ToF AMS data were highly correlated with independent measurements of submicron aerosol volume and dry extinction. There are emissions of several secondary aerosol precursors in the Houston area: sulfur dioxide (SO2) from industrial facilities and isolated power plants as well as volatile organic compounds (VOCs) from industrial facilities mainly along the ship channel and from other urban sources. Downwind of Houston, there is a clear progression of increasing aerosol mass as a function of distance, with both sulfate and organic material being formed. However, the complexity of the Houston area sources produces an inhomogeneous composition of the aerosol downwind, also depending on the upwind source. Since the sources of SOA (secondary organic aerosol) precursors cover a large area whereas SO2 is emitted from point sources, the urban area generally produces broadly distributed SOA with narrow, high mass concentrations of sulfate aerosol in the first several hours downwind. In contrast, Dallas is more typical of urban areas with VOCs from mobile emissions as the main precursor of secondary aerosol. Hence, downwind of Dallas the aerosol is more homogeneous in composition and primarily organic. The hygroscopic and optical properties of the aerosol, as it is transformed downwind of both urban areas, will also be discussed.

A24C-05 

Gas-to-Particle Conversion: Observations of Ammonium Nitrate Formation Above Houston

* Nowak, J B (John.Nowak@noaa.gov), Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, United States * Nowak, J B (John.Nowak@noaa.gov), NOAA, Earth System Research Laboratory, Chemical Sciences Division, 325 Broadway, Boulder, CO 80305, United States Neuman, J A (Andy.Neuman@noaa.gov), Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, United States Neuman, J A (Andy.Neuman@noaa.gov), NOAA, Earth System Research Laboratory, Chemical Sciences Division, 325 Broadway, Boulder, CO 80305, United States Bahreini, R (Roya.Bahreini@noaa.gov), Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, United States Bahreini, R (Roya.Bahreini@noaa.gov), NOAA, Earth System Research Laboratory, Chemical Sciences Division, 325 Broadway, Boulder, CO 80305, United States Brock, C A (Charles.A.Brock@noaa.gov), NOAA, Earth System Research Laboratory, Chemical Sciences Division, 325 Broadway, Boulder, CO 80305, United States Middlebrook, A M (Ann.M.Middlebrook@noaa.gov>), NOAA, Earth System Research Laboratory, Chemical Sciences Division, 325 Broadway, Boulder, CO 80305, United States Wollny, A (Adam.Wollny@noaa.gov), Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, United States Wollny, A (Adam.Wollny@noaa.gov), NOAA, Earth System Research Laboratory, Chemical Sciences Division, 325 Broadway, Boulder, CO 80305, United States Holloway, J S (John.S.Holloway@noaa.gov), Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, United States Holloway, J S (John.S.Holloway@noaa.gov), NOAA, Earth System Research Laboratory, Chemical Sciences Division, 325 Broadway, Boulder, CO 80305, United States Peischl, J (Jeff.Peischl@noaa.gov), Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, United States Peischl, J (Jeff.Peischl@noaa.gov), NOAA, Earth System Research Laboratory, Chemical Sciences Division, 325 Broadway, Boulder, CO 80305, United States Ryerson, T B (Thomas.B.Ryerson@noaa.gov), NOAA, Earth System Research Laboratory, Chemical Sciences Division, 325 Broadway, Boulder, CO 80305, United States Fehsenfeld, F C (Fred.C.Fehsenfeld@noaa.gov), Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, United States Fehsenfeld, F C (Fred.C.Fehsenfeld@noaa.gov), NOAA, Earth System Research Laboratory, Chemical Sciences Division, 325 Broadway, Boulder, CO 80305, United States

Ammonium nitrate aerosol is formed from the reaction of gas phase ammonia (NH₃) and nitric acid (HNO₃). Anthropogenic emissions of NH₃ and NOx (NO + NO₂), which is oxidized to form HNO₃, can react to form ammonium nitrate aerosol. Ammonium nitrate formation was observed from the NOAA WP3 aircraft over Houston during the TexAQS/GoMACCS 2006 study with fast-response measurements of NH₃, HNO₃, particle composition, and particle size distribution. Typically, NH₃ mixing ratios over the urban area ranged from 0.2 to 3 ppbv. However, several plumes with high NH₃ levels were sampled on different flights. NH₃ mixing ratios in these plumes ranged from 5 to over 50 ppbv. The high NH₃ mixing ratios shifted the equilibrium to conditions favorable for the formation of ammonium nitrate during the daytime. In these plumes, the NH₃ enhancement correlated with a decrease in HNO₃ mixing ratio and an increase in particulate NO₃^- concentration indicating ammonium nitrate formation. Particle size distribution and aerosol composition data will be analyzed to assess the quantitative agreement between the gas-phase and aerosol observations. Finally, the relationship between these plumes and the location of known NH₃ sources will be examined.

A24C-06 

Carbonaceous Aerosol Processing in the Mexico City Metropolitan Area

* Onasch, T B (onasch@aerodyne.com), Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821, United States Slowik, J G (jslowik@chem.utoronto.ca), University of Toronto, Lash Miller Chemical Laboratories 80 St. George St., Toronto, ON M5S 3H6, Canada Davidovits, P (paul.davidovits@bc.edu), Boston College, 140 Commonwealth Avenue, Chestnut Hill, MA 02467, United States Herndon, S (herndon@aerodyne.com), Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821, United States Wood, E (ezrawood@aerodyne.com), Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821, United States Canagaratna, M (mrcana@aerodyne.com), Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821, United States Worsnop, D (worsnop@aerodyne.com), Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821, United States Kolb, C E (kolb@aerodyne.com), Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821, United States Knighton, B (bknighton@chemistry.montana.edu), Montana State University, PO Box 173400, Bozeman, MT 59717, United States Zavala, M (miguelz@MIT.EDU), Massachusetts Institute of Technology, 77 Massachusetts avenue, Cambridge, MA 02139, United States Thornhill, D (munchie@vt.edu), Virginia Polytechnic Institute and State University, 411 Durham Hall, Blacksburg, VA 24061, Marr, L (lmarr@vt.edu), Virginia Polytechnic Institute and State University, 411 Durham Hall, Blacksburg, VA 24061, Arnott, P (patarnott@physics.unr.edu), Desert Research Institute of the Nevada System of Higher Education, Northern Nevada Science Center, 2215 Raggio Parkway, Reno, NV 89512, United States Mazzoleni, C (claudio@lanl.gov), Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545, United States Dubey, M K (dubey@lanl.gov), Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545, United States Hopkins, R (RJHopkins@lbl.gov), Lawrence Berkeley National Laboratory, One Cyclotron Road BLDG 6R2100, Berkeley, CA 94720, United States Gilles, M K (MKGilles@lbl.gov), Lawrence Berkeley National Laboratory, One Cyclotron Road BLDG 6R2100, Berkeley, CA 94720, United States Desyaterik, Y (yury.desyaterik@pnl.gov), Pacific Northwest National Laboratory, P.O. Box 999, K8-88, Richland, WA 99352, United States Laskin, A (Alexander.Laskin@pnl.gov), Pacific Northwest National Laboratory, P.O. Box 999, K8-88, Richland, WA 99352, United States Kroll, J (kroll@aerodyne.com), Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821, United States

Mexico City Metropolitan Area (MCMA) is a mega-city environment with significant air pollution. Emissions of primary particles and secondary particle precursors are high and build up in the boundary layer during the night with the concentrations peaking during the early morning. Daily photochemistry alters the chemical, physical, and optical properties of these primary particles. The Aerodyne mobile laboratory, outfitted with a suite of gas and particle instruments, investigated the processing of these primary particles at the T0 site as part of the Mexico City Metropolitan Area (MCMA) component of the MILAGRO campaign (March 2006). Aerosol particle mass, chemistry (bulk and surface PAHs), absorption and scattering, and size-distributions (mobility and vacuum aerodynamic) were measured. Simultaneous measurements by the AMS and SMPS instruments on mobility-selected particles yielded the particle mass, volume, density, composition, dynamic shape factor, and fractal dimension. Early morning primary particle emissions were dominated by fractal particles containing significant surface bound PAHs, similar in morphology and composition to diesel-generated particles. During the morning, these particles were observed to grow in mass and become more spherical via gas-to-particle condensation of photochemical products (oxidized organic compounds and ammonium nitrate). Particles with fractal morphologies and surface bound PAH signals were no longer evident after late morning and at down wind locations. Emission ratios, correlations with carbon monoxide, and organic aerosol chemical classifications will be presented. The rapid processing and fate of these primary particles will be discussed with an emphasis on gaining insight into the processing mechanisms.

A24C-07 

Comparison of Urban and Biogenic Influences on Aerosol Composition at a Semirural Site in Southern Ontario

* Slowik, J (jslowik@chem.utoronto.ca), University of Toronto, Lash Miller Chemical Laboratories, 80 St. George St., Toronto, ON M5S 3H6, Canada Vlasenko, A (avlasenk@chem.utoronto.ca), University of Toronto, Lash Miller Chemical Laboratories, 80 St. George St., Toronto, ON M5S 3H6, Canada Chang, R (rchang@chem.utoronto.ca), University of Toronto, Lash Miller Chemical Laboratories, 80 St. George St., Toronto, ON M5S 3H6, Canada Sjostedt, S (ssjosted@chem.utoronto.ca), University of Toronto, Lash Miller Chemical Laboratories, 80 St. George St., Toronto, ON M5S 3H6, Canada Shantz, N (nshantz@chem.utoronto.ca), University of Toronto, Lash Miller Chemical Laboratories, 80 St. George St., Toronto, ON M5S 3H6, Canada Leaitch, R (Richard.Leaitch@ec.gc.ca), Environment Canada, 4905 Dufferin St., Downsview, ON M3H 5T4, Canada Macdonald, A (AnneMarie.Macdonald@ec.gc.ca), Environment Canada, 4905 Dufferin St., Downsview, ON M3H 5T4, Canada Toom-Sauntry, D (Desiree.Toom-Sauntry@ec.gc.ca), Environment Canada, 4905 Dufferin St., Downsview, ON M3H 5T4, Canada Abbatt, J (jabbatt@chem.utoronto.ca), University of Toronto, Lash Miller Chemical Laboratories, 80 St. George St., Toronto, ON M5S 3H6, Canada

Intensive gas and particle measurements were conducted at the Center for Atmospheric Research Experiments (CARE) in Egbert, Ontario, as part of the Egbert 2007 summer field campaign. The CARE site is located approximately 70 km north of Toronto and is influenced both by urban outflow and biogenic emissions. As such, this location offers an ideal venue to compare the contributions of anthropogenic and biogenic sources to the aerosol at a semirural location. Mass spectra from an Aerodyne time-of-flight mass spectrometer (AMS) were deconvolved into factors related to chemical composition and emissions sources using positive matrix factorization. Factors were obtained relating to anthropogenic and biogenic secondary organic aerosol (SOA) formation, as well as processed and unprocessed primary anthropogenic emissions. Correlation of these factors with measurements of VOC concentrations by a proton transfer mass spectrometer (PTRMS) and a Hantsch monitor enables the factors to be interpreted in terms of the photochemical age of the particles and the gaseous precursors and/or reaction byproducts relating to particle sources and processing. In addition to the organic species, the urban outflow yielded high concentrations of particulate sulfate and a prominent diurnal cycle of nitrate concentrations, peaking shortly before dawn. Due to the complexity of the sources influencing the CARE site, particle mixing state is important in determining source contributions. The mixing state was determined from the AMS single particle mass spectra, triggered by signals from an optical scattering module. AMS collection efficiency, which is related to particle phase, was estimated by comparison with a Particle-Into- Liquid-Sampler (PILS) system.

A24C-08 

Fast airborne aerosol size and composition measurements from the NCAR C-130 during the MIRAGE-Mex 2006 field campaign

* DeCarlo, P F (decarlop@colorado.edu), CIRES, University of Colorado, 216 UCB, Boulder, CO 80309, United States * DeCarlo, P F (decarlop@colorado.edu), Dept of Atmospheric and Oceanic Science, Univ. of Colorado, 318 UCB, Boulder, CO 80309, United States Dunlea, E (edward.dunlea@colorado.edu), CIRES, University of Colorado, 216 UCB, Boulder, CO 80309, United States Kimmel, J (joel.kimmel@colorado.edu), CIRES, University of Colorado, 216 UCB, Boulder, CO 80309, United States Ulbrich, I (Ingrid.Ulbrich@Colorado.EDU), CIRES, University of Colorado, 216 UCB, Boulder, CO 80309, United States Ulbrich, I (Ingrid.Ulbrich@Colorado.EDU), Dept. of Chemistry, Univ. of Colorado, 215 UCB, Boulder, CO 80309, United States Aiken, A (allison.aiken@colorado.edu), CIRES, University of Colorado, 216 UCB, Boulder, CO 80309, United States Aiken, A (allison.aiken@colorado.edu), Dept. of Chemistry, Univ. of Colorado, 215 UCB, Boulder, CO 80309, United States Crounse, J (crounjd@caltech.edu), Geology and Planetary Science, California Inst. of Tech., MC 170-25 1200 E. California Blvd., Pasadena, CA 91125, United States Wennberg, P (wennberg@gps.caltech.edu), Geology and Planetary Science, California Inst. of Tech., MC 170-25 1200 E. California Blvd., Pasadena, CA 91125, United States Shinozuka, Y (yohei@hawaii.edu), Department of Oceanography, University of Hawaii, 1000 Pope Rd, Honolulu, HI 96822, United States Clarke, T (tclarke@soest.hawaii.edu), Department of Oceanography, University of Hawaii, 1000 Pope Rd, Honolulu, HI 96822, United States Zhao, J (jczhou@hawaii.edu), Department of Oceanography, University of Hawaii, 1000 Pope Rd, Honolulu, HI 96822, United States Tomlinson, J (jason.tomlinson@tamu.edu), Dept. of Atm. Sci., College of Geosciences, Texas A&M Univ., 3150 TAMU, College Station, TX 77843, United States Collins, D (dcollins@tamu.edu), Dept. of Atm. Sci., College of Geosciences, Texas A&M Univ., 3150 TAMU, College Station, TX 77843, United States Campos, T (campos@ucar.edu), NCAR, PO Box 3000, Boulder, CO 80307, United States Jimenez, J L (jose.jimenez@colorado.edu), CIRES, University of Colorado, 216 UCB, Boulder, CO 80309, United States Jimenez, J L (jose.jimenez@colorado.edu), Dept. of Chemistry, Univ. of Colorado, 215 UCB, Boulder, CO 80309, United States

A high mass resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS, DeCarlo et al., 2006) was deployed for the first time on an airborne platform during the MIRAGE-Mex campaign on the NCAR C-130 research aircraft, for measurements of size-resolved non-refractory sulfate, nitrate, ammonium, chloride, and organics. Onboard the C-130 the HR-ToF-AMS was operated in a medium resolution mode known as "V-ToF mode", providing added chemical resolution of the measured aerosol, while still maintaining good spatial (time) resolution and allowing the measurement of size distributions. Organic aerosol (OA) accounted for approximately half of the non-refractory submicron aerosol mass and showed strong correlation with gas phase measurements of CO and HCN. Due to the strong correlations with HCN and CO, the sources of organic aerosol are thought to be a combination of biomass burning, transportation and other urban combustion sources, and (pollution-related) secondary OA (SOA). High-resolution OA mass spectra were also analyzed with the Positive Matrix Factorization algorithm, including periods with high and low regional biomass burning (BB) as determined by satellite fire counts and tracers. Four dominant OA components were extracted. Three oxidized organic aerosol components, termed oxygenated OA 1 and 2 (OOA-1, OOA-2) and biomass burning OA (BBOA) were obtained, along with a reduced "hydrocarbon-like" (HOA) component. OOA-1 is linked to regional airmasses and highly oxidized and aged organic aerosol. Based on absolute levels and correlations with tracers in high vs. low fire periods, the majority (total to 2/3) attributed to anthropogenic sources and up to 1/3 estimated to come from BB during periods of high burning activity. OOA-2 appears to be a fresh SOA strongly correlated with ammonium nitrate, and the Mexico City Basin. The similar correlation with tracers in both flights strongly indicates an urban origin, and during low fires periods it is the largest OA component in the Mexico City basin. BBOA is identified as biomass burning aerosol due to a strong correlation with HCN, and the presence of marker ions such as C2H4O2+ and C3H5O2+ (m/z 60 and 73 markers for Levoglucosan). At times when burning activity is high, BBOA makes a large contribution to OA mass in the basin and contributes strongly to the mass in the outflow. This component is small (~10%) during periods of low BB activity. Comparing to measurements in the city basin (T0, Aiken et al., this conference) the BBOA observed in the C-130 has increased oxidation. This may be due to SOA formation from BB precursors, or to a Robinson-like evaporation-oxidation-repartitioning mechanism (Robinson et al., Science, 2007), since fresh BBOA in Mexico is very volatile (Huffman et al., this conference).

Author(s) (2007), Title, Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract #####-##.