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| Titel |
Polar organic marker compounds in atmospheric aerosols during the LBA-SMOCC 2002 biomass burning experiment in Rondônia, Brazil: sources and source processes, time series, diel variations and size distributions |
| VerfasserIn |
M. Claeys, I. Kourtchev, V. Pashynska, G. Vas, R. Vermeylen, W. Wang, J. Cafmeyer, X. Chi, P. Artaxo, M. O. Andreae, W. Maenhaut |
| 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 ; 10, no. 19 ; Nr. 10, no. 19 (2010-10-05), S.9319-9331 |
| Datensatznummer |
250008803
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| Publikation (Nr.) |
 copernicus.org/acp-10-9319-2010.pdf |
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| Zusammenfassung |
| Measurements of polar organic marker compounds were performed on aerosols
that were collected at a pasture site in the Amazon basin (Rondônia,
Brazil) using a high-volume dichotomous sampler (HVDS) and a Micro-Orifice
Uniform Deposit Impactor (MOUDI) within the framework of the 2002 LBA-SMOCC
(Large-Scale Biosphere Atmosphere Experiment in Amazônia – Smoke
Aerosols, Clouds, Rainfall, and Climate: Aerosols From Biomass Burning
Perturb Global and Regional Climate) campaign. The campaign spanned the late dry
season (biomass burning), a transition period, and the onset of the wet season (clean conditions). In the present study a more
detailed discussion is presented compared to previous reports on the
behavior of selected polar marker compounds, including levoglucosan, malic
acid, isoprene secondary organic aerosol (SOA) tracers and tracers for
fungal spores. The tracer data are discussed taking into account new
insights that recently became available into their stability and/or aerosol
formation processes. During all three periods, levoglucosan was the most
dominant identified organic species in the PM2.5 size fraction of the
HVDS samples. In the dry period levoglucosan reached concentrations of up to
7.5 μg m−3 and exhibited diel variations with a nighttime
prevalence. It was closely associated with the PM mass in the
size-segregated samples and was mainly present in the fine mode, except
during the wet period where it peaked in the coarse mode. Isoprene SOA
tracers showed an average concentration of 250 ng m−3 during the dry
period versus 157 ng m−3 during the transition period and 52 ng m−3
during the wet period. Malic acid and the 2-methyltetrols
exhibited a different size distribution pattern, which is consistent with
different aerosol formation processes (i.e., gas-to-particle partitioning in
the case of malic acid and heterogeneous formation from gas-phase precursors
in the case of the 2-methyltetrols). The 2-methyltetrols were mainly
associated with the fine mode during all periods, while malic acid was
prevalent in the fine mode only during the dry and transition periods, and
dominant in the coarse mode during the wet period. The sum of the fungal
spore tracers arabitol, mannitol, and erythritol in the PM2.5 fraction
of the HVDS samples during the dry, transition, and wet periods was, on
average, 54 ng m−3, 34 ng m−3, and 27 ng m−3, respectively,
and revealed minor day/night variation. The mass size distributions of
arabitol and mannitol during all periods showed similar patterns and an
association with the coarse mode, consistent with their primary origin. The
results show that even under the heavy smoke conditions of the dry period a
natural background with contributions from bioaerosols and isoprene SOA can
be revealed. The enhancement in isoprene SOA in the dry season is mainly
attributed to an increased acidity of the aerosols, increased NOx
concentrations and a decreased wet deposition. |
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