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| Titel |
Observations and analysis of organic aerosol evolution in some prescribed fire smoke plumes |
| VerfasserIn |
A. A. May, T. Lee, G. R. McMeeking, S. Akagi, A. P. Sullivan, S. Urbanski, R. J. Yokelson, S. M. Kreidenweis |
| 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. 11 ; Nr. 15, no. 11 (2015-06-11), S.6323-6335 |
| Datensatznummer |
250119800
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| Publikation (Nr.) |
 copernicus.org/acp-15-6323-2015.pdf |
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| Zusammenfassung |
| Open biomass burning is a significant source of primary air pollutants such as particulate matter (PM)
and non-methane organic gases (NMOG). However, the physical and chemical
atmospheric processing of these emissions during transport is poorly
understood. Atmospheric transformations of biomass burning emissions have
been investigated in environmental chambers, but there have been limited
opportunities to investigate these transformations in the atmosphere. In this
study, we deployed a suite of real-time instrumentation on a Twin Otter
aircraft to sample smoke from prescribed fires in South Carolina, conducting
measurements at both the source and downwind to characterize smoke evolution
with atmospheric aging. Organic aerosol (OA) within the smoke plumes was
quantified using an aerosol mass spectrometer (AMS); refractory black carbon
(rBC) was quantified using a single-particle soot photometer, and carbon
monoxide (CO) and carbon dioxide (CO2) were measured using a cavity
ring-down spectrometer. During the two fires for which we were able to obtain
aerosol aging data, normalized excess mixing ratios and "export factors" of
conserved species (rBC, CO, CO2) suggested that changes in emissions at
the source did not account for most of the differences observed in samples of
increasing age. An investigation of AMS mass fragments indicated that the
in-plume fractional contribution (fm/z) to OA of the primary fragment
(m/z 60) decreased downwind, while the fractional contribution of the
secondary fragment (m/z 44) increased. Increases in f44 are typically
interpreted as indicating chemical aging of OA. Likewise, we observed an
increase in the O : C elemental ratio downwind, which is usually associated
with aerosol aging. However, the rapid mixing of these plumes into the
background air suggests that these chemical transformations may be
attributable to the different volatilities of the compounds that fragment to
these m/z in the AMS. The gas–particle partitioning behavior of the bulk
OA observed during the study was consistent with the predictions from a
parameterization developed for open biomass burning emissions in the
laboratory. Furthermore, we observed no statistically significant increase in
total organic mass with atmospheric transport. Hence, our results suggest
that dilution-driven evaporation likely dominated over the chemical
production of secondary organic aerosol (SOA) within our smoke plumes,
presumably due to the fast dilution and limited aging times
(< ~ 5 h) that we could sample. |
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