Airborne determination of the temporo-spatial distribution of benzene, toluene, nitrogen oxides and ozone in the boundary layer across Greater London, UK

Shaw, Marvin and Lee, J. D. and Davison, B. and Vaughan, A. and Purvis, R. M. and Lewis, A. C. and Hewitt, C. N. (2014) Airborne determination of the temporo-spatial distribution of benzene, toluene, nitrogen oxides and ozone in the boundary layer across Greater London, UK. Atmospheric Chemistry and Physics Discussions, 14 (19). pp. 27335-27371. ISSN 1680-7367

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Abstract

Highly spatially resolved mixing ratios of benzene and toluene, nitrogen oxides (NOx) and ozone (O3) were measured in the atmospheric boundary layer above Greater London during the period 24 June to 9 July 2013 using a Dornier 228 aircraft. Toluene and benzene were determined in-situ using a proton transfer reaction mass spectrometer (PTR-MS), NOx by dual channel NOx chemiluminescence and O3 mixing ratios by UV absorption. Average mixing ratios observed over inner London at 360 ± 10 m a.g.l. were 0.20 ± 0.05, 0.28 ± 0.07, 13.2 ± 8.6, 21.0 ± 7.3 and 34.3 ± 15.2 ppbv for benzene, toluene, NO, NO2 and NOx respectively. Linear regression analysis between NO2, benzene and toluene mixing ratios yielded a trimodal distribution indicating that these compounds predominantly share the same or co-located sources within the city and that a significant fraction of NOx is directly emitted as NO2. Average mixing ratios measured at 360 ± 10 m a.g.l. over outer London were always lower than over inner London. Where traffic densities were highest, the toluene $/$ benzene (T / B) concentration ratios were highest (average of 1.8 ± 0.3 ppbv ppbv−1) indicative of strong local sources. Daytime maxima in NOx, benzene and toluene mixing ratios were observed in the morning (~40 ppbv NOx, ~350 pptv toluene and ~200 pptv benzene) and for ozone in the mid-afternoon (~40 ppbv O3) all at 360 ± 10 m a.g.l.

Item Type:
Journal Article
Journal or Publication Title:
Atmospheric Chemistry and Physics Discussions
Additional Information:
Date of Acceptance: 15/10/2014
ID Code:
73395
Deposited By:
Deposited On:
18 Jun 2015 05:37
Refereed?:
Yes
Published?:
Published
Last Modified:
16 May 2020 04:12