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| Titel |
Properties and evolution of biomass burning organic aerosol from Canadian boreal forest fires |
| VerfasserIn |
M. D. Jolleys, H. Coe, G. McFiggans, J. W. Taylor, S. J. O'Shea, M. Le Breton, S. J.-B. Bauguitte, S. Moller, P. Di Carlo, E. Aruffo, P. I. Palmer, J. D. Lee, C. J. Percival, M. W. Gallagher |
| 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. 6 ; Nr. 15, no. 6 (2015-03-18), S.3077-3095 |
| Datensatznummer |
250119559
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| Publikation (Nr.) |
 copernicus.org/acp-15-3077-2015.pdf |
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| Zusammenfassung |
| Airborne measurements of biomass burning organic aerosol (BBOA) from boreal
forest fires reveal highly contrasting properties for plumes of different
ages. These measurements, performed using an Aerodyne Research Inc. compact
time-of-flight aerosol mass spectrometer (C-ToF-AMS) during the BORTAS
(quantifying the impact of BOReal forest fires on Tropospheric oxidants over
the Atlantic using Aircraft and Satellites) experiment in the summer of 2011,
have been used to derive normalised excess organic aerosol (OA) mass
concentrations (ΔOA / ΔCO), with higher average ratios observed closer to
source (0.190±0.010) than in the far-field (0.097±0.002). The
difference in ΔOA / ΔCO between fresh and aged plumes is
influenced by a change in dominant combustion conditions throughout the
campaign. Measurements at source comprised 3 plume interceptions during a
single research flight and sampled largely smouldering fires. Twenty-three
interceptions were made across four flights in the far-field, with plumes
originating from fires occurring earlier in the campaign when fire activity
had been more intense, creating an underlying contrast in emissions prior to
any transformations associated with aging. Changing combustion conditions
also affect the vertical distribution of biomass burning emissions, as aged
plumes from more flaming-dominated fires are injected to higher altitudes of
up to 6000 m. Proportional contributions of the mass-to-charge ratio
(m/z) 60 and 44 peaks in the AMS mass spectra to the total OA mass
(denoted f60 and f44) are used as tracers for primary and oxidised
BBOA, respectively. f44 is lower on average in near-field plumes than
those sampled in the far-field, in accordance with longer aging times as
plumes are transported a greater distance from source. However, high levels
of ΔO3 / ΔCO and
−log(NOx / NOy) close to source indicate that
emissions can be subject to very rapid oxidation over short timescales.
Conversely, the lofting of plumes into the upper troposphere can lead to the
retention of source profiles after transportation over extensive temporal and
spatial scales, with f60 also higher on average in aged plumes.
Evolution of OA composition with aging is comparable to observations of BB
tracers in previous studies, revealing a consistent progression from f60
to f44. The elevated levels of oxygenation in aged plumes, and their
association with lower average ΔOA / ΔCO, are consistent
with OA loss through evaporation during aging due to a combination of
dilution and chemical processing, while differences in combustion conditions
throughout the campaign also have a significant influence on BBOA production
and composition. |
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