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| Titel |
Biomass burning emissions of trace gases and particles in marine air at Cape Grim, Tasmania |
| VerfasserIn |
S. J. Lawson, M. D. Keywood, I. E. Galbally, J. L. Gras, J. M. Cainey, M. E. Cope, P. B. Krummel, P. J. Fraser, L. P. Steele, S. T. Bentley, C. P. Meyer, Z. Ristovski, A. H. Goldstein |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 23 ; Nr. 15, no. 23 (2015-12-07), S.13393-13411 |
| Datensatznummer |
250120202
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| Publikation (Nr.) |
 copernicus.org/acp-15-13393-2015.pdf |
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| Zusammenfassung |
Biomass burning (BB) plumes were measured at the Cape Grim Baseline Air
Pollution Station during the 2006 Precursors to Particles campaign, when
emissions from a fire on nearby Robbins Island impacted the station.
Measurements made included non-methane organic compounds (NMOCs) (PTR-MS),
particle number size distribution, condensation nuclei (CN)
> 3 nm, black carbon (BC) concentration, cloud condensation nuclei
(CCN) number, ozone (O3), methane (CH4), carbon monoxide
(CO), hydrogen (H2), carbon dioxide (CO2), nitrous oxide
(N2O), halocarbons and meteorology.
During the first plume strike event (BB1), a 4 h enhancement of CO (max
~ 2100 ppb), BC (~ 1400 ng m-3) and particles
> 3 nm (~ 13 000 cm-3) with dominant particle
mode of 120 nm were observed overnight. A wind direction change lead
to a dramatic reduction in BB tracers and a drop in the dominant particle
mode to 50 nm. The dominant mode increased in size to 80 nm
over 5 h in calm sunny conditions, accompanied by an increase in
ozone. Due to an enhancement in BC but not CO during particle growth, the
presence of BB emissions during this period could not be confirmed.
The ability of particles > 80 nm (CN80) to act as CCN at 0.5 %
supersaturation was investigated. The ΔCCN / ΔCN80 ratio was
lowest during the fresh BB plume (56 ± 8 %), higher during the
particle growth period (77 ± 4 %) and higher still (104 ± 3 %)
in background marine air. Particle size distributions indicate that changes
to particle chemical composition, rather than particle size, are driving
these changes. Hourly average CCN during both BB events were between 2000 and
5000 CCN cm-3, which were enhanced above typical background
levels by a factor of 6–34, highlighting the dramatic impact BB plumes can
have on CCN number in clean marine regions.
During the 29 h of the second plume strike event (BB2) CO, BC and a
range of NMOCs including acetonitrile and hydrogen cyanide (HCN) were clearly
enhanced and some enhancements in O3 were observed
(ΔO3 / ΔCO 0.001–0.074). A short-lived increase in NMOCs by
a factor of 10 corresponded with a large CO enhancement, an increase of the
NMOC / CO emission ratio (ER) by a factor of 2–4 and a halving of the
BC / CO ratio. Rainfall on Robbins Island was observed by radar during
this period which likely resulted in a lower fire combustion efficiency, and
higher emission of compounds associated with smouldering. This highlights the
importance of relatively minor meteorological events on BB emission ratios.
Emission factors (EFs) were derived for a range of trace gases, some never
before reported for Australian fires, (including hydrogen, phenol and
toluene) using the carbon mass balance method. This provides a unique set of
EFs for Australian coastal heathland fires. Methyl halide EFs were higher than
EFs reported from other studies in Australia and the Northern Hemisphere which
is likely due to high halogen content in vegetation on Robbins Island.
This work demonstrates the substantial impact that BB plumes can have on the
composition of marine air, and the significant changes that can occur as the
plume interacts with terrestrial, aged urban and marine emission sources. |
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