Low-NO atmospheric oxidation pathways in a polluted megacity

Newland, Mike J.; Bryant, Daniel J.; Dunmore, Rachel E.; Bannan, Thomas J.; Acton, W. Joe F.; Langford, Ben ORCID: https://orcid.org/0000-0002-6968-5197; Hopkins, James R.; Squires, Freya A.; Dixon, William; Drysdale, William S.; Ivatt, Peter D.; Evans, Mathew J.; Edwards, Peter M.; Whalley, Lisa K.; Heard, Dwayne E.; Slater, Eloise J.; Woodward-Massey, Robert; Ye, Chunxiang; Mehra, Archit; Worrall, Stephen D.; Bacak, Asan; Coe, Hugh; Percival, Carl J.; Hewitt, C. Nicholas; Lee, James D.; Cui, Tianqu; Surratt, Jason D.; Wang, Xinming; Lewis, Alastair C.; Rickard, Andrew R.; Hamilton, Jacqueline F.. 2021 Low-NO atmospheric oxidation pathways in a polluted megacity [in special issue: In-depth study of air pollution sources and processes within Beijing and its surrounding region (APHH-Beijing) (ACP/AMT inter-journal SI)] Atmospheric Chemistry and Physics, 21 (3). 1613-1625. 10.5194/acp-21-1613-2021

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Abstract/Summary

The impact of emissions of volatile organic compounds (VOCs) to the atmosphere on the production of secondary pollutants, such as ozone and secondary organic aerosol (SOA), is mediated by the concentration of nitric oxide (NO). Polluted urban atmospheres are typically considered to be “high-NO” environments, while remote regions such as rainforests, with minimal anthropogenic influences, are considered to be “low NO”. However, our observations from central Beijing show that this simplistic separation of regimes is flawed. Despite being in one of the largest megacities in the world, we observe formation of gas- and aerosol-phase oxidation products usually associated with low-NO “rainforest-like” atmospheric oxidation pathways during the afternoon, caused by extreme suppression of NO concentrations at this time. Box model calculations suggest that during the morning high-NO chemistry predominates (95 %) but in the afternoon low-NO chemistry plays a greater role (30 %). Current emissions inventories are applied in the GEOS-Chem model which shows that such models, when run at the regional scale, fail to accurately predict such an extreme diurnal cycle in the NO concentration. With increasing global emphasis on reducing air pollution, it is crucial for the modelling tools used to develop urban air quality policy to be able to accurately represent such extreme diurnal variations in NO to accurately predict the formation of pollutants such as SOA and ozone.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.5194/acp-21-1613-2021
UKCEH and CEH Sections/Science Areas:	Atmospheric Chemistry and Effects (Science Area 2017-)
ISSN:	1680-7316
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
NORA Subject Terms:	Atmospheric Sciences
Date made live:	28 Apr 2020 13:55 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/527561

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