Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 14, 6677-6693, 2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
02 Jul 2014
The impact of monoaromatic hydrocarbons on OH reactivity in the coastal UK boundary layer and free troposphere
R. T. Lidster1, J. F. Hamilton1, J. D. Lee1,2, A. C. Lewis1,2, J. R. Hopkins1,2, S. Punjabi1, A. R. Rickard1,2, and J. C. Young3 1The Department of Chemistry, The University of York, Heslington, UK
2National Centre for Atmospheric Science, University of York, Heslington, York, UK
3School of Chemistry, University of Leeds, Leeds, UK
Abstract. Reaction with the hydroxyl radical (OH) is the dominant removal mechanism for virtually all volatile organic compounds (VOCs) in the atmosphere; however, it can be difficult to reconcile measured OH reactivity with known sinks. Unresolved higher molecular weight VOCs contribute to OH sinks, of which monoaromatics are potentially an important sub-class. A method based on comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC × GC-TOFMS) has been developed that extends the degree with which larger VOCs can be individually speciated from whole air samples (WAS). The technique showed excellent sensitivity, resolution and good agreement with an established gas chromatography–flame ionisation (GC-FID) method, for compounds amenable to analysis on both instruments. Measurements have been made of VOCs within the UK east coast marine boundary layer and free troposphere, using samples collected from five aircraft flights in winter 2011. Ten monoaromatic compounds with an array of different alkyl ring substituents have been quantified, in addition to the simple aromatics, benzene, toluene, ethyl benzene and Σm- and p-xylene. These additional compounds were then included in constrained box model simulations of atmospheric chemistry occurring at two UK rural and suburban field sites in order to assess the potential impact of these larger monoaromatics species on OH reactivity; they have been calculated to contribute an additional 2–6% to the overall modelled OH loss rate, providing a maximum additional OH sink of ~0.9 s−1.

Citation: Lidster, R. T., Hamilton, J. F., Lee, J. D., Lewis, A. C., Hopkins, J. R., Punjabi, S., Rickard, A. R., and Young, J. C.: The impact of monoaromatic hydrocarbons on OH reactivity in the coastal UK boundary layer and free troposphere, Atmos. Chem. Phys., 14, 6677-6693,, 2014.
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