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Published August 9, 2022 | Supplemental Material + Published
Journal Article Open

Heterogeneous iodine-organic chemistry fast-tracks marine new particle formation


The gas-phase formation of new particles less than 1 nm in size and their subsequent growth significantly alters the availability of cloud condensation nuclei (CCN, >30–50 nm), leading to impacts on cloud reflectance and the global radiative budget. However, this growth cannot be accounted for by condensation of typical species driving the initial nucleation. Here, we present evidence that nucleated iodine oxide clusters provide unique sites for the accelerated growth of organic vapors to overcome the coagulation sink. Heterogeneous reactions form low-volatility organic acids and alkylaminium salts in the particle phase, while further oligomerization of small α-dicarbonyls (e.g., glyoxal) drives the particle growth. This identified heterogeneous mechanism explains the occurrence of particle production events at organic vapor concentrations almost an order of magnitude lower than those required for growth via condensation alone. A notable fraction of iodine associated with these growing particles is recycled back into the gas phase, suggesting an effective transport mechanism for iodine to remote regions, acting as a "catalyst" for nucleation and subsequent new particle production in marine air.

Additional Information

© 2022 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND). Edited by Akkihebbal Ravishankara, Colorado State University, Fort Collins, CO; received January 30, 2022; accepted June 14, 2022. Received: January 30, 2022. Accepted: June 14, 2022. Published online: August 2, 2022. Published in issue: August 9, 2022. The authors gratefully acknowledge the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model used in this publication. This work was supported by the National Natural Science Foundation of China (41925015), the Key Research Program of Frontier Sciences from the Chinese Academy of Sciences (ZDBS-LY-DQC001), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB40000000), SKLLQG (SKLLQGTD1801), the European Union's Seventh Framework Programme (FP7/2007-2013) project BACCHUS under grant agreement 603445, the Irish Environmental Protection Agency, the HEA PRTLI4 project, and MaREI, the SFI (Science Foundation Ireland) Research Centre for Energy, Climate and Marine. This article is a PNAS Direct Submission. Data Availability. All study data are included in the article and/or SI Appendix. Data related to this article are also available at the East Asian Paleoenvironmental Science Database, National Earth System Science Data Center, National Science & Technology Infrastructure of China (http://paleodata.ieecas.cn/index.aspx) (48). Author contributions: R.-J.H., T.H., and C.O. designed research; R.-J.H., J.O., Wen Xu, and D.C. performed research; R.Z. contributed new reagents/analytic tools; R.-J.H., J.O., A.L., H.K., Wei Xu, and D.C. analyzed data; and R.-J.H., T.H., J.H.S., and C.O. wrote the paper. The authors declare no competing interest.

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August 22, 2023
October 24, 2023