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Title	The gas-phase formation mechanism of iodic acid as an atmospheric aerosol source
Author(s)	Finkenzeller, Henning (Colorado U. ; Colorado U., CIRES) ; Iyer, Siddharth (Tampere U. of Tech.) ; He, Xu-Cheng (Helsinki U.) ; Simon, Mario (Goethe U., Frankfurt (main)) ; Koenig, Theodore K (Colorado U. ; Colorado U., CIRES ; Peking U., Beijing) ; Lee, Christopher F (Colorado U. ; Colorado U., CIRES) ; Valiev, Rashid (Helsinki U.) ; Hofbauer, Victoria (Carnegie Mellon U.) ; Amorim, Antonio (Lisbon U.) ; Baalbaki, Rima (Helsinki U.) ; Baccarini, Andrea (PSI, Villigen ; LPHE, Lausanne) ; Beck, Lisa (Helsinki U.) ; Bell, David M (PSI, Villigen) ; Caudillo, Lucía (Goethe U., Frankfurt (main)) ; Chen, Dexian (Carnegie Mellon U.) ; Chiu, Randall (Colorado U. ; Colorado U., CIRES) ; Chu, Biwu (Helsinki U. ; Beijing, Inst. High Energy Phys.) ; Dada, Lubna (Helsinki U. ; PSI, Villigen) ; Duplissy, Jonathan (Helsinki U. ; Helsinki Inst. of Phys.) ; Heinritzi, Martin (Goethe U., Frankfurt (main)) ; Kemppainen, Deniz (Helsinki U.) ; Kim, Changhyuk (Pusan Natl. U. ; Caltech) ; Krechmer, Jordan (New England Nucl.) ; Kürten, Andreas (Goethe U., Frankfurt (main)) ; Kvashnin, Alexandr (Lebedev Inst.) ; Lamkaddam, Houssni (PSI, Villigen) ; Lee, Chuan Ping (PSI, Villigen) ; Lehtipalo, Katrianne (Helsinki U. ; Finnish Meteorological Inst.) ; Li, Zijun (Aalto U.) ; Makhmutov, Vladimir (Lebedev Inst. ; Moscow, MIPT) ; Manninen, Hanna E (CERN) ; Marie, Guillaume (Goethe U., Frankfurt (main)) ; Marten, Ruby (PSI, Villigen) ; Mauldin, Roy L (Colorado U. ; Carnegie Mellon U.) ; Mentler, Bernhard (Innsbruck U.) ; Müller, Tatjana (Goethe U., Frankfurt (main)) ; Petäjä, Tuukka (Helsinki U.) ; Philippov, Maxim (Lebedev Inst.) ; Ranjithkumar, Ananth (Leeds U., Math.) ; Rörup, Birte (Helsinki U.) ; Shen, Jiali (Helsinki U.) ; Stolzenburg, Dominik (Helsinki U. ; Vienna U.) ; Tauber, Christian (Vienna U.) ; Tham, Yee Jun (Helsinki U. ; Zhongshan U., Zhuhai) ; Tomé, António (Beira Interior U., Covilha) ; Vazquez-Pufleau, Miguel (Vienna U.) ; Wagner, Andrea C (Colorado U. ; Colorado U., CIRES ; Goethe U., Frankfurt (main)) ; Wang, Dongyu S (PSI, Villigen) ; Wang, Mingyi (Caltech) ; Wang, Yonghong (Helsinki U. ; Beijing, Inst. High Energy Phys.) ; Weber, Stefan K (Goethe U., Frankfurt (main) ; CERN) ; Nie, Wei (Nanjing U. (main)) ; Wu, Yusheng (Helsinki U.) ; Xiao, Mao (PSI, Villigen) ; Ye, Qing (Carnegie Mellon U.) ; Zauner-Wieczorek, Marcel (Goethe U., Frankfurt (main)) ; Hansel, Armin (Innsbruck U.) ; Baltensperger, Urs (PSI, Villigen) ; Brioude, Jérome (CNAM, Paris) ; Curtius, Joachim (Goethe U., Frankfurt (main)) ; Donahue, Neil M (Carnegie Mellon U.) ; Haddad, Imad El (PSI, Villigen) ; Flagan, Richard C (Caltech) ; Kulmala, Markku (Helsinki U. ; Nanjing U. (main) ; CICQM, Beijing) ; Kirkby, Jasper (Goethe U., Frankfurt (main) ; CERN) ; Sipilä, Mikko (Helsinki U.) ; Worsnop, Douglas R (Helsinki U. ; New England Nucl.) ; Kurten, Theo (Helsinki U.) ; Rissanen, Matti (Tampere U. of Tech.) ; Volkamer, Rainer (Colorado U. ; Colorado U., CIRES)
Publication	2022
Number of pages	7
In:	Nature Chem. 15 (2022) 129-135
DOI	10.1038/s41557-022-01067-z
Subject category	Chemical Physics and Chemistry
Abstract	AbstractIodine is a reactive trace element in atmospheric chemistry that destroys ozone and nucleates particles. Iodine emissions have tripled since 1950 and are projected to keep increasing with rising O3 surface concentrations. Although iodic acid (HIO3) is widespread and forms particles more efficiently than sulfuric acid, its gas-phase formation mechanism remains unresolved. Here, in CLOUD atmospheric simulation chamber experiments that generate iodine radicals at atmospherically relevant rates, we show that iodooxy hypoiodite, IOIO, is efficiently converted into HIO3 via reactions (R1) IOIO + O3 → IOIO4 and (R2) IOIO4 + H2O → HIO3 + HOI + (1)O2. The laboratory-derived reaction rate coefficients are corroborated by theory and shown to explain field observations of daytime HIO3 in the remote lower free troposphere. The mechanism provides a missing link between iodine sources and particle formation. Because particulate iodate is readily reduced, recycling iodine back into the gas phase, our results suggest a catalytic role of iodine in aerosol formation.
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