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Download Abstracts Here - IGAC Project

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List of <strong>Abstracts</strong> 151P-Transformation.54 ID:4198 10:30Total OH reactivity of vehicular exhaust with a chassis dynamometerYoshizumi Kajii 1 , Yoshihiro Nakashima 1 , Shungo Kato 1 , Shinji Kobayashi 21 Tokyo Metropolitan University2 National Institute for Environmental StudiesContact: kajii@tmu.ac.jpTotal OH reactivity for exhaust gas of gasoline vehicles was measured under nine different drivingconditions with a chassis dynamometer at the National Institute for Environmental Studies. Analyses of tracespecies including 50 kinds of VOCs and NOx as well as OH reactivity were carried out. The chemicalcompositions of vehicular exhaust were found to depend on the temperature of the engine or catalysts. Forall driving cycles, the calculated OH reactivity was confirmed to be underestimated, implying the existenceof unknown species in the exhaust gas. The percentage contribution of OH reactivity to the unknown speciesduring “Cold” start was about 17.5%, which was almost the same as that for “Hot” start at 17.0%. However,the absolute value of OH reactivity for “Cold” start was about ten times higher than that for “Hot” start.P-Transformation.55 ID:4332 10:30Modelling Atmospheric OH-reactivityDitte Mogensen 1 , Sampo Smolander 1 , Vinayak Sinha 2 , Jonathan Williams 2 , Michael Boy 11 The University of Helsinki2 Max Planck Insitute of ChemistryContact: dittemogensen@gmail.comAs the focus on climate, air quality, visibility and public health has increased, so has the research onsecondary organic aerosol (SOA) formation. SOAs are formed from atmospheric oxidation of volatileorganic compounds (VOCs). The hydroxyl radical (OH) is the most important oxidant of the atmosphere,and knowledge of the atmospheric concentration and lifetime of OH is necessary to further theunderstanding of the SOA formation. However, the overall OH sink term is currently poorly constrained inmodels in the absence of direct measurements of the OH radical and its total OH-reactivity. A betterunderstanding of the OH-reactivity is needed. We have modelled the atmospheric OH-reactivity in a borealforest and investigated the contributions from atmospheric inorganic species, methane, isoprene,monoterpenes and other important VOCs. We have used SOSA; a one dimensional vertical chemistrytransportmodel together with measured data from Hyytiälä, SMEAR II station, Southern Finland, August2008. In order to ascertain how well we understand the OH initiated photochemical processes, we havecompared our calculated OH-reactivity with measured ambient OH-reactivity from the BFORM (BorealForest OH Reactivity Measurements) campaign, August 2008. <strong>Here</strong> the total atmospheric OH-reactivity wasmeasured using the the Comparative Reactivity Method (Sinha et al., 2008, ACP). We found that thesimulated OH-reactivity underestimates the measurements by about 30%. This was expected due to thethousands of unknown organic compounds not included in our model simulations. In this work we will showhow much different individual compounds contribute to the total measured OH-reactivity. Reference: Sinha,V., Williams, J., Crowley, J. N. & Lelievold, J. (2008). Atmos. Chem. Phys, 8, 2213-2227.P-Transformation.56 ID:4305 10:30Hydroxyl radical in the troposphere: lessons learned from methyl chloroform simulationsPrabir Patra 1 , Maarten Krol 2 , Masayuki Takigawa 1 , Tim Arnold 3 , Ray Weiss 3 , James Elkins, StephenMontzka 4 , Paul Fraser, Paul Krummel 5 , Shyam Lal 6 , Simon O'Doherty, Peter Simmonds 7 , Ronald Prinn 81 RIGC/JAMSTECiCACGP-<strong>IGAC</strong> 2010 14 July, 2010

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