Molecular understanding of the suppression of new-particle formation by isoprene

Martin Heinritzi (1) , Lubna Dada (2) , Mario Simon (1) , Dominik Stolzenburg (3) , Andrea C Wagner (1, 4) , Lukas Fischer (5) , Lauri R Ahonen (2) , Stavros Amanatidis (6) , Rima Baalbaki (2) , Andrea Baccarini (7) , Paulus S Bauer (3) , Bernhard Baumgartner (3) , Federico Bianchi (2, 8) , Sophia Brilke (3) , Dexian Chen (9) , Randall Chiu (4) , Antonio Dias (10, 11) , Josef Dommen (7) , Jonathan Duplissy (2) , Henning Finkenzeller (4) , Carla Frege (7) , Claudia Fuchs (7) , Olga Garmash (2) , Hamish Gordon (11, 12) , Manuel Granzin (1) , Imad El Haddad (7) , Xucheng He (2) , Johanna Helm (1) , Victoria Hofbauer (9) , Christopher R Hoyle (13) , Juha Kangasluoma (2, 8) , Timo Keber (1) , Changhyuk Kim (6, 14) , Andreas Kürten (1) , Houssni Lamkaddam (7) , Tiia M Laurila (2) , Janne Lampilahti (2) , Chuan Ping Lee (7) , Katrianne Lehtipalo (2) , Markus Leiminger (5) , Huajun Mai (6) , Vladimir Makhmutov (15) , Hanna Elina Manninen (11) , Ruby Marten (7) , Serge Mathot (11) , Roy Lee Mauldin (2, 16, 9) , Bernhard Mentler (5) , Ugo Molteni (7) , Tatjana Müller (1) , Wei Nie (17) , Tuomo Nieminen (18) , Antti Onnela (11) , Eva Partoll (5) , Monica Passananti (2) , Tuukka Petäjä (2) , Joschka Pfeifer (1, 11) , Veronika Pospisilova (7) , Lauriane L J Quéléver (2) , Clémence Rose (19, 2) , Matti P Rissanen , Siegfried Schobesberger , Wiebke Scholz , Kay Scholze , Mikko Sipilä (2) , Gerhard Steiner (5) , Yuri Stozhkov (15) , Christian Tauber (3) , Yee Jun Tham (2) , Miguel Vazquez-Pufleau (3) , Annele Virtanen (18) , Alexander L Vogel (1, 11) , Rainer Volkamer (4) , Robert C Wagner (2) , Mingyi Wang (9) , Lena Weitz (20) , Daniela Wimmer (2) , Mao Xiao (7) , Chao Yan (2) , Penglin Ye (9, 21) , Qiaozhi Zha (2) , Xueqin Zhou (1, 7) , Antonio Amorim (10) , Urs Baltensperger (7) , Armin Hansel (5) , Markku Kulmala (2, 8, 22) , António Tomé (23) , Paul M Winkler (3) , Douglas R Worsnop (2, 21) , Neil M Donahue (9) , Jasper Kirkby (1, 11) , Joachim Curtius (1)

1 IAU - Institute for Atmospheric and Environmental Sciences [Frankfurt/Main]
2 INAR - Institute for Atmospheric and Earth System Research
3 University of Vienna [Vienna]
4 University of Colorado [Boulder]
5 Institut für Ionenphysik und Angewandte Physik - Institute for Ion Physics and Applied Physics [Innsbruck]
6 CALTECH - California Institute of Technology
7 LAC - Laboratory of Atmospheric Chemistry [Paul Scherrer Institute]
8 Beijing University of Chemical Technology
9 CMU - Carnegie Mellon University [Pittsburgh]
10 ULISBOA - Universidade de Lisboa = University of Lisbon
11 CERN [Genève]
12 SEE - School of Earth and Environment [Leeds]
13 IAC - Institute for Atmospheric and Climate Science [Zürich]
14 PNU - Pusan National University
15 LPI RAS - P. N. Lebedev Physical Institute of the Russian Academy of Sciences [Moscow]
16 ATOC - Department of Atmospheric and Oceanic Sciences [Boulder]
17 School of Atmospheric Sciences [Nanjing]
18 University of Eastern Finland
19 LaMP - Laboratoire de météorologie physique
20 IAU - Institut für Atmosphäre und Umwelt [Frankfurt/Main]
21 Aerodyne Research Inc.
22 HIP - Helsinki Institute of Physics
23 UBI - University of Beira Interior [Portugal]

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 oxy-genated products that can nucleate with or without sulfu-ric 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 nu-cleation 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 q) arising from monoterpenes or isoprene. Compared with pure monoterpene conditions, isoprene reduces nucleation rates at 1.7 nm (de-pending 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 iso-prene. We further show that increased hydroxyl radical (OH q) reduces particle formation in our chemical system rather than enhances it as previously proposed, since it increases isoprene-derived RO 2 q radicals that reduce C 20 formation. RO 2 q 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 iso-prene, 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.

Domaines: Physique Atmosphérique et Océanique [physics.ao-ph]; Océan, Atmosphère; Météorologie

Martin Heinritzi, Lubna Dada, Mario Simon, Dominik Stolzenburg, Andrea C Wagner, et al.. Molecular understanding of the suppression of new-particle formation by isoprene. Atmospheric Chemistry and Physics, 2020, 20, pp.11809 - 11821. ⟨10.5194/acp-20-11809-2020⟩. ⟨hal-02996178⟩