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| Titel |
Aerosol and precipitation chemistry measurements in a remote site in Central Amazonia: the role of biogenic contribution |
| VerfasserIn |
T. Pauliquevis, L. L. Lara, M. L. Antunes, P. Artaxo |
| 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 ; 12, no. 11 ; Nr. 12, no. 11 (2012-06-07), S.4987-5015 |
| Datensatznummer |
250011225
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| Publikation (Nr.) |
 copernicus.org/acp-12-4987-2012.pdf |
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| Zusammenfassung |
| In this analysis a 3.5 years data set of
aerosol and precipitation chemistry, obtained in a remote site in Central
Amazonia (Balbina, (1°55' S, 59°29' W, 174 m a.s.l.), about
200 km north of Manaus) is discussed. Aerosols were sampled using stacked filter units
(SFU), which separate fine (d < 2.5 μm) and coarse mode
(2.5 μm < d < 10.0 μm) aerosol particles. Filters were analyzed for
particulate mass (PM), Equivalent Black Carbon (BCE) and elemental
composition by Particle Induced X-Ray Emission (PIXE). Rainwater samples
were collected using a wet-only sampler and samples were analyzed for pH and
ionic composition, which was determined using ionic chromatography (IC).
Natural sources dominated the aerosol mass during the wet season, when it
was predominantly of natural biogenic origin mostly in the coarse mode,
which comprised up to 81% of PM10. Biogenic aerosol from both
primary emissions and secondary organic aerosol dominates the fine mode in
the wet season, with very low concentrations (average 2.2 μg m-3).
Soil dust was responsible for a minor fraction of the aerosol mass (less
than 17%). Sudden increases in the concentration of
elements as Al, Ti and Fe were also observed, both in fine and coarse mode (mostly during the
April-may months), which we attribute to episodes of Saharan dust transport.
During the dry periods, a significant contribution to the
fine aerosols loading was observed, due to the large-scale transport of smoke from biomass
burning in other portions of the Amazon basin. This contribution is
associated with the enhancement of the concentration of S, K, Zn and
BCE. Chlorine, which is commonly associated to sea salt and also to
biomass burning emissions, presented higher concentration not only during
the dry season but also for the April–June months, due to the establishment
of more favorable meteorological conditions to the transport of Atlantic air
masses to Central Amazonia. The chemical composition of rainwater was
similar to those ones observed in other remote sites in tropical forests.
The volume-weighted mean (VWM) pH was 4.90. The most important contribution
to acidity was from weak organic acids. The organic acidity was
predominantly associated with the presence of acetic acid instead of formic acid, which is more often observed in pristine tropical areas. Wet deposition
rates for major species did not differ significantly between dry and wet
season, except for NH4+, citrate and acetate, which had smaller
deposition rates during dry season. While biomass burning emissions were
clearly identified in the aerosol component, it did not present a clear
signature in rainwater. The biogenic component and the long-range transport
of sea salt were observed both in aerosols and rainwater composition. The
results shown here indicate that in Central Amazonia it is still possible to
observe quite pristine atmospheric conditions, relatively free of
anthropogenic influences. |
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