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| Titel |
Seasonal and diurnal trends in concentrations and fluxes of volatile organic compounds in central London |
| VerfasserIn |
A. C. Valach, B. Langford, E. Nemitz, A. R. MacKenzie, C. N. Hewitt |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 14 ; Nr. 15, no. 14 (2015-07-16), S.7777-7796 |
| Datensatznummer |
250119901
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| Publikation (Nr.) |
 copernicus.org/acp-15-7777-2015.pdf |
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| Zusammenfassung |
| Concentrations and fluxes of seven volatile organic compounds (VOCs) were
measured between August and December 2012 at a rooftop site in central
London as part of the ClearfLo project (Clean Air for London). VOC
concentrations were quantified using a proton transfer reaction mass
spectrometer (PTR-MS) and fluxes were calculated using a virtual disjunct
eddy covariance technique. The median VOC fluxes, including
aromatics, oxygenated compounds and isoprene, ranged from 0.07 to 0.33 mg m−2 h−1. Median mixing ratios were 7.3 ppb for methanol and
< 1 ppb for the other compounds. Strong relationships were observed
between the fluxes and concentrations of some VOCs with traffic density and
between the fluxes and concentrations of isoprene and oxygenated compounds
with photosynthetically active radiation (PAR) and temperature. An estimated
50–90 % of the fluxes of aromatic VOCs were attributable to traffic
activity, which showed little seasonal variation, suggesting that boundary
layer effects or possibly advected pollution may be the primary causes of
increased concentrations of aromatics in winter. Isoprene, methanol and
acetaldehyde fluxes and concentrations in August and September showed high
correlations with PAR and temperature, when fluxes and concentrations were
largest suggesting that biogenic sources contributed to their fluxes.
Modelled biogenic isoprene fluxes from urban vegetation using the Guenther
et al. (1995) algorithm agreed well with measured fluxes in August and
September. Comparisons of estimated annual benzene emissions from both the London
and the National Atmospheric Emissions Inventories agreed well with measured
benzene fluxes. Flux footprint analysis indicated emission sources were
localised and that boundary layer dynamics and source strengths were
responsible for temporal and spatial VOC flux and concentration variability
during the measurement period. |
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