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Low-NO atmospheric oxidation pathways in a polluted megacity

Authors :
M. J. Newland
D. J. Bryant
R. E. Dunmore
T. J. Bannan
W. J. F. Acton
B. Langford
J. R. Hopkins
F. A. Squires
W. Dixon
W. S. Drysdale
P. D. Ivatt
M. J. Evans
P. M. Edwards
L. K. Whalley
D. E. Heard
E. J. Slater
R. Woodward-Massey
C. Ye
A. Mehra
S. D. Worrall
A. Bacak
H. Coe
C. J. Percival
C. N. Hewitt
J. D. Lee
T. Cui
J. D. Surratt
X. Wang
A. C. Lewis
A. R. Rickard
J. F. Hamilton
Source :
Atmospheric Chemistry and Physics, Vol 21, Pp 1613-1625 (2021)
Publication Year :
2021
Publisher :
Copernicus Publications, 2021.

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.

Subjects

Subjects :
Physics
QC1-999
Chemistry
QD1-999

Details

Language :
English
ISSN :
16807316 and 16807324
Volume :
21
Database :
Directory of Open Access Journals
Journal :
Atmospheric Chemistry and Physics
Publication Type :
Academic Journal
Accession number :
edsdoj.b9fb4394f93a4de1940b1eb184c07c30
Document Type :
article
Full Text :
https://doi.org/10.5194/acp-21-1613-2021