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Crilley, LR, Kramer, LJ, Pope, FD et al. (6 more authors) (2021) Is the ocean surface a source of nitrous acid (HONO) in the marine boundary layer? Atmospheric Chemistry and Physics, 21 (24). pp. 18213-18225. ISSN 1680-7316
Abstract
Nitrous acid, HONO, is a key net photolytic precursor to OH radicals in the atmospheric boundary layer. As OH is the dominant atmospheric oxidant, driving the removal of many primary pollutants and the formation of secondary species, a quantitative understanding of HONO sources is important to predict atmospheric oxidising capacity. While a number of HONO formation mechanisms have been identified, recent work has ascribed significant importance to the dark, ocean-surface-mediated conversion of NO₂ to HONO in the coastal marine boundary layer. In order to evaluate the role of this mechanism, here we analyse measurements of HONO and related species obtained at two contrasting coastal locations – Cabo Verde (Atlantic Ocean, denoted Cape Verde herein), representative of the clean remote tropical marine boundary layer, and Weybourne (United Kingdom), representative of semi-polluted northern European coastal waters. As expected, higher average concentrations of HONO (70 ppt) were observed in marine air for the more anthropogenically influenced Weybourne location compared to Cape Verde (HONO < 5 ppt). At both sites, the approximately constant HONO/NO₂ ratio at night pointed to a low importance for the dark, ocean-surface-mediated conversion of NO₂ into HONO, whereas the midday maximum in the HONO/NO₂ ratios indicated significant contributions from photo-enhanced HONO formation mechanisms (or other sources). We obtained an upper limit to the rate coefficient of dark, ocean-surface HONO-to-NO₂ conversion of CHONO = 0.0011 ppb h⁻¹ from the Cape Verde observations; this is a factor of 5 lower than the slowest rate reported previously. These results point to significant geographical variation in the predominant HONO formation mechanisms in marine environments and indicate that caution is required when extrapolating the importance of such mechanisms from individual study locations to assess regional and/or global impacts on oxidising capacity. As a significant fraction of atmospheric processing occurs in the marine boundary layer, particularly in the tropics, better constraint of the possible ocean surface source of HONO is important for a quantitative understanding of chemical processing of primary trace gases in the global atmospheric boundary layer and associated impacts upon air pollution and climate.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > National Centre for Atmos Science (NCAS) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 08 Jun 2023 13:41 |
Last Modified: | 21 Jul 2023 10:45 |
Status: | Published |
Publisher: | Copernicus |
Identification Number: | 10.5194/acp-21-18213-2021 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:200075 |
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Is the ocean surface a source of nitrous acid (HONO) in the marine boundary layer? (deposited 21 Jul 2023 10:35)
- Is the ocean surface a source of nitrous acid (HONO) in the marine boundary layer? (deposited 08 Jun 2023 13:41) [Currently Displayed]