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  Long-term study on coarse mode aerosols in the Amazon rain forest with the frequent intrusion of Saharan dust plumes

Moran-Zuloaga, D., Ditas, F., Walter, D., Saturno, J., Brito, J., Carbone, S., et al. (2017). Long-term study on coarse mode aerosols in the Amazon rain forest with the frequent intrusion of Saharan dust plumes. Atmospheric Chemistry and Physics Discussions, 17. doi:10.5194/acp-2017-1043.

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Moran-Zuloaga, Daniel1, Author              
Ditas, F.1, Author              
Walter, David2, Author              
Saturno, Jorge1, Author              
Brito, Joel, Author
Carbone, Samara, Author
Chi, Xuguang, Author
de Angelis, Isabella Hrabě, Author
Baars, Holger, Author
Godoi, Ricardo H. M., Author
Heese, Birgit, Author
Holanda, Bruna A., Author
Lavrič, Jošt V., Author              
Martin, Scot T., Author
Ming, Jing1, Author              
Pöhlker, Mira L.3, Author              
Ruckteschler, Nina3, Author              
Su, Hang, Author
Wang, Yaquiang, Author
Wang, Qiaoqiao1, Author              
Wang, Zhibin3, Author              Weber, Bettina3, Author              Wolff, Stefan, AuthorArtaxo, Paulo, AuthorPöschl, Ulrich, AuthorAndreae, Meinrat O.1, Author              Pöhlker, Christopher3, Author               more..
1Biogeochemistry, Max Planck Institute for Chemistry, Max Planck Society, ou_1826286              
2Atmospheric Chemistry, Max Planck Institute for Chemistry, Max Planck Society, ou_1826285              
3Multiphase Chemistry, Max Planck Institute for Chemistry, Max Planck Society, ou_1826290              


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 Abstract: In the Amazonian atmosphere, the aerosol coarse mode comprises a complex, diverse, and variable mixture of bioaerosols emitted from the rain forest ecosystem, long-range transported Saharan dust, marine aerosols from the Atlantic Ocean, and coarse smoke particles from deforestation fires. For the rain forest, the coarse mode particles are of significance with respect to biogeochemical and hydrological cycling as well as ecology and biogeography. However, detailed knowledge on the physicochemical and biological properties as well as the ecological role of the Amazonian coarse mode is still sparse. This study presents results from multi-year coarse mode measurements at the remote Amazon Tall Tower Observatory (ATTO) site. It combines online aerosol observations, selected remote sensing and modelling results, as well as dedicated coarse mode sampling and analysis. The focal points of this study are a systematic characterization of aerosol coarse mode abundance and properties in the Amazonian atmosphere as well as a detailed analysis of the frequent, pulse-wise intrusion of African long-range transport (LRT) aerosols (comprising Saharan dust and African biomass burning smoke) into the Amazon Basin. We find that, on a multi-year time scale, the Amazonian coarse mode maintains remarkably constant concentration levels (with 0.4 cm−3 and 4.0 µg m−3 in the wet vs. 1.2 cm−3 and 6.5 µg m−3 in the dry season) with rather weak seasonal trends (in terms of abundance and size spectrum), which is in stark contrast to the pronounced biomass burning-driven seasonality of the submicron aerosol population and related parameters. For most of the time, bioaerosol particles from the forest biome account for a major fraction of the coarse mode background population. However, from Dec to Apr there are episodic intrusions of African LRT aerosols, comprising Saharan dust, sea salt particles from the transatlantic passages, and African biomass burning smoke. Remarkably, during the core period of this LRT season (i.e., Feb–Mar), the presence of LRT influence, occurring as a sequence of pulse-like plumes, appears to be rather the norm than an exception. The LRT pulses increase the coarse mode concentrations drastically (up to 100 µg m−3) and alter coarse mode composition as well as its size spectrum. Efficient transport of the LRT plumes into the Amazon Basin takes place in response to specific mesoscale circulation patterns in combination with the episodic absence of rain-related aerosol scavenging en route. Based on a modelling study, we estimated a dust deposition flux of 5–10 kg ha−1 a−1 in the region of the ATTO site. Furthermore, a chemical analysis quantified the substantial increase of crustal and sea salt elements under LRT conditions in comparison to the background coarse mode composition. With these results, we estimated the deposition fluxes of various elements that are considered as nutrients for the rain forest ecosystem. These estimates range from few g ha−1 a−1 up to several hundreds of g ha−1 a−1 in the ATTO region. The long-term data presented here provide a statistically solid basis for future studies of the manifold aspects of the dynamic coarse mode aerosol cycling in the Amazon. Thus, it may help to understand its biogeochemical relevance in this ecosystem as well as to evaluate to what extent anthropogenic influences have altered the coarse mode cycling already.


Language(s): eng - English
 Dates: 2017
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: No review
 Identifiers: DOI: 10.5194/acp-2017-1043
 Degree: -



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Title: Atmospheric Chemistry and Physics Discussions
  Abbreviation : Atmos. Chem. Phys. Discuss.
Source Genre: Journal
Publ. Info: Katlenburg-Lindau, Germany : European Geophysical Society, Copernicus Publ.
Pages: 52 Volume / Issue: 17 Sequence Number: - Start / End Page: - Identifier: ISSN: 1680-7367
CoNE: https://pure.mpg.de/cone/journals/resource/111076360006006