Low-NO atmospheric oxidation pathways in a polluted megacity

Abstract

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.

Publication DOI: https://doi.org/10.5194/acp-21-1613-2021
Divisions: College of Engineering & Physical Sciences > School of Infrastructure and Sustainable Engineering > Chemical Engineering & Applied Chemistry
College of Engineering & Physical Sciences
Additional Information: © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Funding: This research has been supported by the Natural Environment Research Council and the Newton Fund and Medical Research Council in the UK and by the National Natural Science Foundation of China (grant nos. NE/N007190/1 and NE/N006917/1)
Uncontrolled Keywords: Atmospheric Science
Full Text Link:
Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
PURE Output Type: Article
Published Date: 2021-02-08
Accepted Date: 2020-12-01
Authors: Newland, Mike J.
Bryant, Daniel J.
Dunmore, Rachel E.
Bannan, Thomas J.
Joe, W.
Langford, Ben
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. (ORCID Profile 0000-0003-1969-3671)
Bacak, Asan
Coe, Hugh
Percival, Carl J.
Nicholas Hewitt, C.
Lee, James D.
Cui, Tianqu
Surratt, Jason D.
Wang, Xinming
Lewis, Alastair C.
Rickard, Andrew R.
Hamilton, Jacqueline F.

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