|
Author(s)
|
Heinritzi, Martin (Frankfurt U.) ; Dada, Lubna (Helsinki U.) ; Simon, Mario (Frankfurt U.) ; Stolzenburg, Dominik (Vienna U.) ; Wagner, Andrea C (Frankfurt U. ; U. Colorado, Boulder) ; Fischer, Lukas (Innsbruck U.) ; Ahonen, Lauri R (Helsinki U.) ; Amanatidis, Stavros (Caltech, Pasadena (main)) ; Baalbaki, Rima (Helsinki U.) ; Baccarini, Andrea (PSI, Villigen) ; Bauer, Paulus S (Vienna U.) ; Baumgartner, Bernhard (Vienna U.) ; Bianchi, Federico (Helsinki U. ; Beijing U. of Chem. Tech.) ; Brilke, Sophia (Vienna U.) ; Chen, Dexian (Carnegie Mellon U.) ; Chiu, Randall (U. Colorado, Boulder) ; Dias, Antonio (Lisbon U. ; CERN) ; Dommen, Josef (PSI, Villigen) ; Duplissy, Jonathan (Helsinki U.) ; Finkenzeller, Henning (U. Colorado, Boulder) ; Frege, Carla ; Fuchs, Claudia ; Garmash, Olga ; Gordon, Hamish ; Granzin, Manuel ; El Haddad, Imad ; He, Xucheng ; Helm, Johanna ; Hofbauer, Victoria ; Hoyle, Christopher R ; Kangasluoma, Juha ; Keber, Timo ; Kim, Changhyuk ; Kürten, Andreas ; Lamkaddam, Houssni ; Laurila, Tiia M ; Lampilahti, Janne ; Lee, Chuan Ping ; Lehtipalo, Katrianne ; Leiminger, Markus ; Mai, Huajun ; Makhmutov, Vladimir ; Manninen, Hanna Elina (CERN) ; Marten, Ruby ; Mathot, Serge (CERN) ; Mauldin, Roy Lee ; Mentler, Bernhard ; Molteni, Ugo ; Müller, Tatjana ; Nie, Wei ; Nieminen, Tuomo ; Onnela, Antti ; Partoll, Eva ; Passananti, Monica ; Petäjä, Tuukka ; Pfeifer, Joschka (CERN) ; Pospisilova, Veronika ; Quéléver, Lauriane L J ; Rissanen, Matti P ; Rose, Clémence ; Schobesberger, Siegfried ; Scholz, Wiebke ; Scholze, Kay ; Sipilä, Mikko ; Steiner, Gerhard ; Stozhkov, Yuri ; Tauber, Christian ; Tham, Yee Jun ; Vazquez-Pufleau, Miguel ; Virtanen, Annele ; Vogel, Alexander L ; Volkamer, Rainer ; Wagner, Robert ; Wang, Mingyi ; Weitz, Lena ; Wimmer, Daniela ; Xiao, Mao ; Yan, Chao ; Ye, Penglin ; Zha, Qiaozhi ; Zhou, Xueqin ; Amorim, Antonio ; Baltensperger, Urs ; Hansel, Armin ; Kulmala, Markku ; Tomé, António ; Winkler, Paul M ; Worsnop, Douglas R ; Donahue, Neil M ; Kirkby, Jasper (CERN) ; Curtius, Joachim |
|
Abstract
| Nucleation of atmospheric vapours produces more
than half of global cloud condensation nuclei and so has
an important influence on climate. Recent studies show
that monoterpene (C$_{10}$H$_{16}$) oxidation yields highly oxygenated products that can nucleate with or without sulfuric acid. Monoterpenes are emitted mainly by trees, frequently together with isoprene (C$_5$H$_8$), which has the highest global emission of all organic vapours. Previous studies have shown that isoprene suppresses new-particle formation from monoterpenes, but the cause of this suppression
is under debate. Here, in experiments performed under atmospheric conditions in the CERN CLOUD chamber, we
show that isoprene reduces the yield of highly oxygenated
dimers with 19 or 20 carbon atoms – which drive particle nucleation and early growth – while increasing the production
of dimers with 14 or 15 carbon atoms. The dimers (termed
C$_{20}$ and C$_{15}$, respectively) are produced by termination reactions between pairs of peroxy radicals (RO$_2$) arising from
monoterpenes or isoprene. Compared with pure monoterpene
conditions, isoprene reduces nucleation rates at 1.7 nm (depending on the isoprene / monoterpene ratio) and approximately halves particle growth rates between 1.3 and 3.2 nm.
However, above 3.2 nm, C$_{15}$ dimers contribute to secondary
organic aerosol, and the growth rates are unaffected by isoprene. We further show that increased hydroxyl radical (OH)
reduces particle formation in our chemical system rather
than enhances it as previously proposed, since it increases
isoprene-derived RO$_2$ radicals that reduce C$_{20}$ formation.
RO$_2$ termination emerges as the critical step that determines
the highly oxygenated organic molecule (HOM) distribution
and the corresponding nucleation capability. Species that reduce the C$_{20}$ yield, such as NO, HO$_2$ and as we show isoprene, can thus effectively reduce biogenic nucleation and
early growth. Therefore the formation rate of organic aerosol
in a particular region of the atmosphere under study will vary
according to the precise ambient conditions. |