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Whalley, L orcid.org/0000-0002-4486-9029, Stone, D orcid.org/0000-0001-5610-0463, Bandy, B et al. (6 more authors) (2016) Atmospheric OH reactivity in central London: observations, model predictions and estimates of in situ ozone production. Atmospheric Chemistry and Physics, 16 (4). pp. 2109-2122. ISSN 1680-7316
Abstract
Near-continuous measurements of hydroxyl radical (OH) reactivity in the urban background atmosphere of central London during the summer of 2012 are presented. OH reactivity behaviour is seen to be broadly dependent on air mass origin, with the highest reactivity and the most pronounced diurnal profile observed when air had passed over central London to the east, prior to measurement. Averaged over the entire observation period of 26 days, OH reactivity peaked at ∼ 27 s−1 in the morning, with a minimum of ∼ 15 s−1 during the afternoon. A maximum OH reactivity of 116 s−1 was recorded on one day during morning rush hour. A detailed box model using the Master Chemical Mechanism was used to calculate OH reactivity, and was constrained with an extended measurement data set of volatile organic compounds (VOCs) derived from a gas chromatography flame ionisation detector (GC-FID) and a two-dimensional GC instrument which included heavier molecular weight (up to C12) aliphatic VOCs, oxygenated VOCs and the biogenic VOCs α-pinene and limonene. Comparison was made between observed OH reactivity and modelled OH reactivity using (i) a standard suite of VOC measurements (C2–C8 hydrocarbons and a small selection of oxygenated VOCs) and (ii) a more comprehensive inventory including species up to C12. Modelled reactivities were lower than those measured (by 33 %) when only the reactivity of the standard VOC suite was considered. The difference between measured and modelled reactivity was improved, to within 15 %, if the reactivity of the higher VOCs (⩾ C9) was also considered, with the reactivity of the biogenic compounds of α-pinene and limonene and their oxidation products almost entirely responsible for this improvement. Further improvements in the model's ability to reproduce OH reactivity (to within 6 %) could be achieved if the reactivity and degradation mechanism of unassigned two-dimensional GC peaks were estimated. Neglecting the contribution of the higher VOCs (⩾ C9) (particularly α-pinene and limonene) and model-generated intermediates increases the modelled OH concentrations by 41 %, and the magnitude of in situ ozone production calculated from the production of RO2 was significantly lower (60 %). This work highlights that any future ozone abatement strategies should consider the role that biogenic emissions play alongside anthropogenic emissions in influencing London's air quality.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © Author(s) 2016. This work is distributed under the Creative Commons Attribution 3.0 License |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemistry (Leeds) > Physical Chemistry (Leeds) |
Funding Information: | Funder Grant number NERC (Natural Environment Research Council) NE/J008990/1 NERC (Natural Environment Research Council) NE/H003193/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 10 Mar 2016 12:45 |
Last Modified: | 23 Nov 2022 11:53 |
Published Version: | http://dx.doi.org/10.5194/acp-16-2109-2016 |
Status: | Published |
Publisher: | European Geosciences Union (EGU) |
Identification Number: | 10.5194/acp-16-2109-2016 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:95948 |
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Atmospheric OH reactivity in central London: observations, model predictions and estimates of in situ ozone production. (deposited 23 Nov 2022 14:37)
- Atmospheric OH reactivity in central London: observations, model predictions and estimates of in situ ozone production. (deposited 10 Mar 2016 12:45) [Currently Displayed]