Gomez Martin, JC, Lewis, TR, James, AD orcid.org/0000-0003-0532-0065 et al. (2 more authors) (2022) Insights into the chemistry of iodine new particle formation: the role of iodine oxides and the source of iodic acid. Journal of the American Chemical Society, 144 (21). pp. 9240-9253. ISSN 0002-7863
Abstract
Iodine chemistry is an important driver of new particle formation in the marine and polar boundary layers. There are, however, conflicting views about how iodine gas-to-particle conversion proceeds. Laboratory studies indicate that the photooxidation of iodine produces iodine oxides (IxOy), which are well-known particle precursors. By contrast, nitrate anion chemical ionization mass spectrometry (CIMS) observations in field and environmental chamber studies have been interpreted as evidence of a dominant role of iodic acid (HIO₃) in iodine-driven particle formation. Here, we report flow tube laboratory experiments that solve these discrepancies by showing that both IxOy and HIO₃ are involved in atmospheric new particle formation. I₂Oy molecules (y = 2, 3, and 4) react with nitrate core ions to generate mass spectra similar to those obtained by CIMS, including the iodate anion. Iodine pentoxide (I₂O₅) produced by photolysis of higher-order IxOy is hydrolyzed, likely by the water dimer, to yield HIO₃, which also contributes to the iodate anion signal. We estimate that ∼50% of the iodate anion signals observed by nitrate CIMS under atmospheric water vapor concentrations originate from I₂Oy. Under such conditions, iodine-containing clusters and particles are formed by aggregation of I₂Oy and HIO₃, while under dry laboratory conditions, particle formation is driven exclusively by I₂Oy. An updated mechanism for iodine gas-to-particle conversion is provided. Furthermore, we propose that a key iodine reservoir species such as iodine nitrate, which we observe as a product of the reaction between iodine oxides and the nitrate anion, can also be detected by CIMS in the atmosphere.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2022 The Authors. Published by American Chemical Society. This is an open access article under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemistry (Leeds) > Physical Chemistry (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 13 May 2022 13:57 |
Last Modified: | 17 Feb 2023 16:10 |
Status: | Published |
Publisher: | American Chemical Society |
Identification Number: | 10.1021/jacs.1c12957 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:186762 |