Airborne determination of the temporo-spatial distribution of benzene, toluene, nitrogen oxides and ozone in the boundary layer across Greater London, UK
Highly spatially resolved mixing ratios of benzene and toluene, nitrogen oxides (NO<sub><i>x</i></sub>) and ozone (O<sub>3</sub>) were measured in the atmospheric boundary layer above Greater London during the period 24 June to 9 July 2013 using a Dornier 228 airc...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-05-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/15/5083/2015/acp-15-5083-2015.pdf |
| Summary: | Highly spatially resolved mixing ratios of benzene and toluene, nitrogen
oxides (NO<sub><i>x</i></sub>) and ozone (O<sub>3</sub>) 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), NO<sub><i>x</i></sub> by dual-channel NO<sub><i>x</i></sub> chemiluminescence and O<sub>3</sub> mixing
ratios by UV absorption.
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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, NO<sub>2</sub> and NO<sub><i>x</i></sub>
respectively. Linear regression analysis between NO<sub>2</sub>, benzene and
toluene mixing ratios yields a strong covariance, indicating that these
compounds predominantly share the same or co-located sources within the
city.
<br><br>
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 ± 0.5 ppbv ppbv<sup>-1</sup>), indicative of strong local
sources. Daytime maxima in NO<sub><i>x</i></sub>, benzene and toluene mixing ratios were
observed in the morning (~ 40 ppbv NO<sub><i>x</i></sub>, ~ 350 pptv toluene and ~ 200 pptv benzene) and in the
mid-afternoon for ozone (~ 40 ppbv O<sub>3</sub>), all at 360 ± 10 m a.g.l. |
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| ISSN: | 1680-7316 1680-7324 |