Fluxes and concentrations of volatile organic compounds above central London, UK 1Lancaster Environment Centre, Lancaster University, LA1 4YQ, Lancaster, UK
2Biogeochemistry Programme, Centre for Ecology and Hydrology (Edinburgh), Bush Estate, EH26 0QB, Penicuik, UK
3School of Chemistry, Edinburgh University, West Mains Road, EH9 3JJ, Edinburgh, UK
4National Centre for Atmospheric Science, University of York, YO10 5DD, York, UK
Received: 03 July 2009 – Published in Atmos. Chem. Phys. Discuss.: 14 August 2009 Abstract. Concentrations and fluxes of eight volatile organic compounds (VOCs) were
measured during October 2006 from a high telecom tower above central London,
as part of the CityFlux contribution to the REPARTEE I campaign. A
continuous flow disjunct eddy covariance technique with analysis by proton
transfer reaction mass spectrometry was used. Daily averaged VOC mixing
ratios were within the range 1–19 ppb for the oxygenated compounds
(methanol, acetaldehyde and acetone) and 0.2–1.3 ppb for the aromatics
(benzene, toluene and C2-benzenes). Typical VOC fluxes were in the
range 0.1–1.0 mg m−2 h−1. There was a non-linear relationship
between VOC fluxes and traffic density for most of the measured compounds.
Traffic activity was estimated to account for approximately 70% of the
aromatic compound fluxes, whereas non-traffic related sources were found to
be more important for methanol and isoprene fluxes. The measured fluxes were
comparable to the estimates of the UK national atmospheric emission
inventory for the aromatic VOCs and CO. In contrast, fluxes of the
oxygenated compounds were about three times larger than inventory estimates.
For isoprene and acetonitrile this difference was many times larger. At
temperatures over 25° C it is estimated that more than half the
isoprene observed in central London is of biogenic origin.
Revised: 11 December 2009 – Accepted: 08 January 2010 – Published: 22 January 2010
Citation: Langford, B., Nemitz, E., House, E., Phillips, G. J., Famulari, D., Davison, B., Hopkins, J. R., Lewis, A. C., and Hewitt, C. N.: Fluxes and concentrations of volatile organic compounds above central London, UK, Atmos. Chem. Phys., 10, 627-645, doi:10.5194/acp-10-627-2010, 2010.