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The changing oxidizing environment in London – trends in ozone precursors and their contribution to ozone production

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journal contribution
posted on 12.12.2016, 16:35 by E. von Schneidemesser, M. Vieno, P. S. Monks
Ground-level ozone is recognized to be a threat to human health (WHO, 2003), have a deleterious impact on vegetation (Fowler et al., 2009), is also an important greenhouse gas (IPCC, 2007) and key to the oxidative ability of the atmosphere (Monks et al., 5 2009). Owing to its harmful effect on health, much policy and mitigation effort has been put into reducing its precursors – the nitrogen oxides (NOx ) and non-methane volatile organic compounds (NMVOCs). The non-linear chemistry of tropospheric ozone formation, dependent mainly on NOx and NMVOC concentrations in the atmosphere, makes controlling tropospheric ozone complex. Furthermore, the concentration of ozone at 10 any given point is a complex superimposition of in-situ produced or destroyed ozone and transported ozone on the regional and hemispheric-scale. In order to effectively address ozone, a more detailed understanding of its origins is needed. Here we show that roughly half (5 µgm−3 ) of the observed increase in urban (London) ozone (10 µgm−3 ) in the UK from 1998 to 2008 is owing to factors of local origin, in particular, the change in NO : NO2 15 ratio, NMVOC : NOx balance, NMVOC speciation, and emission reductions (including NOx titration). In areas with previously higher large concentrations of nitrogen oxides, ozone that was previously suppressed by high concentrations of NO has now been “unmasked”, as in London and other urban areas of the UK. The remaining half (approximately 5 µgm−3 ) of the observed ozone increase is attributed to non-local 20 factors such as long-term transport of ozone, changes in background ozone, and meteorological variability. These results show that a two-pronged approach, local action and regional-to-hemispheric cooperation, is needed to reduce ozone and thereby population exposure, which is especially important for urban ozone.

Funding

This study was funded in part by the European Commission under the seventh framework programme as part of the CityZen project (212095), as well as Pegasos (FP7-ENV-2010-265148). The UK monitoring network and data were supported by the Air and 20 Environmental Quality Division of the Department for Environment, Food, and Rural Affairs.

History

Citation

Atmospheric Chemistry and Physics Discussions (2014) 14, 1287-1316

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING

Version

VoR (Version of Record)

Published in

Atmospheric Chemistry and Physics Discussions (2014) 14

Publisher

European Geosciences Union (EGU), Copernicus Publications

issn

1680-7367

eissn

1680-7375

Acceptance date

23/12/2013

Copyright date

2014

Available date

12/12/2016

Publisher version

http://www.atmos-chem-phys-discuss.net/acp-2013-926/

Notes

Supplementary material related to this article is available online at 15 http://www.atmos-chem-phys-discuss.net/14/1287/2014/ acpd-14-1287-2014-supplement.pdf.

Language

en

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