Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 118, Issue 4, Pages -Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.2009951118
Keywords
iodine; heterogeneous reaction; halogen recycling; ozone loss
Categories
Funding
- Academy of Finland [3282290, 306853, 296628, 310626, 315203, 311932, 299574, 326437, 307537, 316114, 326948]
- Jane and Aatos Erkko Foundation
- European Research Council Executive Agency under the European Union's Horizon 2020 Research and Innovation Programme (Project ERC-2016-COG) [726349]
- European Research Council [714621]
- European Research Council via Atmospheric Gas-to-Particle conversion (ATM-GTP) [742206, 266]
- H2020 European Research Council [CHAPAs [850614]]
- European Union [654109]
- EPA-Ireland, Department of Communications, Climate Action and Environment
- COST Action [CA16109]
- MaREI
- SFI Research Centre for Energy, Climate and Marine
- Academy of Finland (AKA) [315203, 310626, 306853, 326948, 310626, 315203, 326948, 306853] Funding Source: Academy of Finland (AKA)
- European Research Council (ERC) [714621, 726349] Funding Source: European Research Council (ERC)
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Reactive iodine, specifically hypoiodous acid (HOI), and interhalogen products (e.g., ICI and IBr), were directly observed in a midlatitude coastal environment, showing faster formation and photolysis rates than previously believed. The photolysis of ICI and IBr increased atomic iodine production rate by 32%, leading to a 10-20% enhancement in daytime average iodine-catalyzed ozone loss rate. These findings highlight the importance of autocatalytic iodine release from marine aerosols in the atmosphere and its impact on atmospheric oxidation capacity.
Reactive iodine plays a key role in determining the oxidation capacity, or cleansing capacity, of the atmosphere in addition to being implicated in the formation of new particles in the marine boundary layer. The postulation that heterogeneous cycling of reactive iodine on aerosols may significantly influence the lifetime of ozone in the troposphere not only remains poorly understood but also heretofore has never been observed or quantified in the field. Here, we report direct ambient observations of hypoiodous acid (HOI) and heterogeneous recycling of interhalogen product species (i.e., iodine monochloride [ICI] and iodine monobromide [IBr]) in a midlatitude coastal environment. Significant levels of ICI and IBr with mean daily maxima of 4.3 and 3.0 parts per trillion by volume (1-min average), respectively, have been observed throughout the campaign. We show that the heterogeneous reaction of HOI on marine aerosol and subsequent production of iodine interhalogens are much faster than previously thought. These results indicate that the fast formation of iodine interhalogens, together with their rapid photolysis, results in more efficient recycling of atomic iodine than currently considered in models. Photolysis of the observed ICI and IBr leads to a 32% increase in the daytime average of atomic iodine production rate, thereby enhancing the average daytime iodine-catalyzed ozone loss rate by 10 to 20%. Our findings provide direct field evidence that the autocatalytic mechanism of iodine release from marine aerosol is important in the atmosphere and can have significant impacts on atmospheric oxidation capacity.
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