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Author(s)
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Molteni, Ugo (PSI, Villigen) ; Simon, Mario (Frankfurt U.) ; Heinritzi, Martin (Frankfurt U.) ; Hoyle, Christopher R (PSI, Villigen) ; Bernhammer, Anne-Kathrin (Ionicon GesmbH, Innsbruck) ; Bianchi, Federico (Helsinki U.) ; Breitenlechner, Martin (Innsbruck U.) ; Brilke, Sophia (Frankfurt U.) ; Dias, António (Lisbon U.) ; Duplissy, Jonathan (Helsinki U. ; Helsinki Inst. of Phys.) ; Frege, Carla (PSI, Villigen) ; Gordon, Hamish (Leeds U.) ; Heyn, Claudia (PSI, Villigen) ; Jokinen, Tuija (Helsinki U.) ; Kürten, Andreas (Frankfurt U.) ; Lehtipalo, Katrianne (Helsinki U. ; Finnish Meteorological Inst.) ; Makhmutov, Vladimir (Lebedev Inst.) ; Petäjä, Tuukka (Helsinki U.) ; Pieber, Simone M (Zurich, ETH) ; Praplan, Arnaud P (Finnish Meteorological Inst.) ; Schobesberger, Siegfried (Helsinki U. ; UEF, Kuopio) ; Steiner, Gerhard (Innsbruck U.) ; Stozhkov, Yuri (Lebedev Inst.) ; Tomé, António (Beira Interior U., Covilha) ; Tröstl, Jasmin (PSI, Villigen) ; Wagner, Andrea C (Frankfurt U.) ; Wagner, Robert (Helsinki U.) ; Williamson, Christina (Frankfurt U.) ; Yan, Chao (Helsinki U.) ; Baltensperger, Urs (PSI, Villigen) ; Curtius, Joachim (Frankfurt U.) ; Donahue, Neil M (Carnegie Mellon U.) ; Hansel, Armin (Innsbruck U.) ; Kirkby, Jasper (Frankfurt U. ; CERN) ; Kulmala, Markku (Helsinki U. ; Helsinki Inst. of Phys. ; Beijing U. of Chem. Tech.) ; Worsnop, Douglas R (Helsinki U. ; Aerodyne Research, Billerica) ; Dommen, Josef (PSI, Villigen) |
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Abstract
| Terpenes are emitted by vegetation, and their oxidation in the
atmosphere is an important source of secondary organic aerosol (SOA). A part of
this oxidation can proceed through an autoxidation process, yielding highly
oxygenated organic molecules (HOMs) with low saturation vapor pressure. They
can therefore contribute, even in the absence of sulfuric acid, to new particle
formation (NPF). The understanding of the autoxidation mechanism and its
kinetics is still far from complete. Here, we present a mechanistic and kinetic
analysis of mass spectrometry data from α-pinene (AP) ozonolysis experiments
performed during the CLOUD 8 campaign at CERN. We grouped HOMs in
classes according to their identified chemical composition and investigated the relative changes of these groups and their components as a function of the reagent concentration. We determined reaction rate constants for the different HOM peroxy
radical reaction pathways. The accretion reaction between HOM peroxy radicals was found to be extremely fast. We developed
a pseudo-mechanism for HOM formation and added it to the AP oxidation scheme of the Master Chemical Mechanism
(MCM). With this extended model, the observed concentrations and trends in HOM formation were successfully simulated. |