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Discussion papers
https://doi.org/10.5194/acp-2018-1067
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-2018-1067
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 15 Oct 2018

Research article | 15 Oct 2018

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This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).

Single-particle characterization of aerosols collected at a remote site in the Amazonian rainforest and an urban site in Manaus, Brazil

Li Wu1, Xue Li1, Hye Kyeong Kim1, Hong Geng2, Ricardo H. M. Godoi3, Cybelli G. G. Barbosa3, Ana F. L. Godoi3, Carlos I. Yamamoto4, Rodrigo A. F. de Souza5, Christopher Pöhlker6, Meinrat O. Andreae6,7, and Chul-Un Ro1 Li Wu et al.
  • 1Department of Chemistry, Inha University, Incheon, 402-751, Korea
  • 2Institute of Environmental Science, Shanxi University, Taiyuan 030006, China
  • 3Environmental Engineering Department, Federal University of Parana-UFPR , Curitiba, PR, Brazil
  • 4Chemical Engineering Department, Federal University of Paraná-UFPR, Curitiba, PR, Brazil
  • 5Amazonas State University, Superior School of Technology, Manaus, Amazonas, Brazil
  • 6Multiphase Chemistry & Biogeochemistry Departments, Max Planck Institute for Chemistry, 55020 Mainz, Germany
  • 7Department of Geology and Geophysics, King Saud University, Riyadh, Saudi Arabia

Abstract. In this study, aerosol samples collected at a remote site in the Amazonian rainforest and an urban site in Manaus, Brazil, were investigated on a single particle basis using a quantitative energy-dispersive electron probe X-ray microanalysis (ED-EPMA). Twenty-three aerosol samples were collected in four size ranges (0.25–0.5, 0.5–1.0, 1.0–2.0, and 2.0–4.0µm) during the wet season in 2012 at two Amazon basin sites: 10 samples in Manaus, an urban area; and 13 samples at an 80-m high tower, located at the Amazon Tall Tower Observatory (ATTO) site in the middle of the rainforest, 150km northeast of Manaus. The aerosol particles were classified into nine particle types based on the morphology on the secondary electron images (SEIs) together with the elemental concentrations of 3,162 individual particles: (i) secondary organic aerosols (SOA), (ii) ammonium sulfate (AS), (iii) SOA and AS mixtures, (iv) aged mineral dust, (v) reacted sea-salts, (vi) primary biological aerosol (PBA), (vii) carbon-rich or elemental carbon (EC) particles, such as soot, tar ball, and char, (viii) fly ash, and (ix) heavy metal (HM, such as Fe, Zn, Ni, and Ti)-containing particles. In submicron aerosols collected at the ATTO site, SOA and AS mixture particles were predominant (50–94% in relative abundance) with SOA and ammonium sulfate comprising 73–100%. In supermicron aerosols at the ATTO site, aged mineral dust and sea-salts (37–70%) as well as SOA and ammonium sulfate (28–58%) were abundant. PBAs were observed abundantly in the PM2–4 fraction (46%), and EC and fly ash particles were absent in all size fractions. The analysis of a bulk PM0.25–0.5 aerosol sample from the ATTO site using Raman microspectrometry and attenuated total reflection Fourier transform infrared spectroscopy showed that ammonium sulfate, organics, and minerals are the major chemical species, which is consistent with the ED-EPMA results. In the submicron aerosols collected in Manaus, either SOA and ammonium sulfate (17–80%) or EC particles (6–78%) were dominant depending on the samples. In contrast, aged mineral dust, reacted sea-salt, PBA, SOA, ammonium sulfate, and EC particles comprised most of the supermicron aerosols collected in Manaus. The SOA, ammonium sulfate, and PBAs were mostly of a biogenic origin from the rainforest, whereas the EC and HM-containing particles were of an anthropogenic origin. Aged mineral dust and reacted sea-salt particles, including mineral dust mixed with sea-salts probably during long-range transatlantic transport, were abundant in the supermicron fractions at both sites. Among the aged mineral dust and reacted sea-salt particles, sulfate-containing ones outnumbered those containing nitrates and sulfate+nitrate in the ATTO samples. In contrast, particles containing sulfate+nitrate were comparable in number to particles containing sulfate only in the Manaus samples, indicating the different sources and formation mechanisms of secondary aerosols, i.e., the predominant presence of sulfate at the ATTO site from mostly biogenic emissions and the elevated influences of nitrates from anthropogenic activities at the Manaus site.

Li Wu et al.
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Aerosol samples collected at a remote site in the Amazonian rainforest (ATTO) and an urban site in Manaus, Brazil, were investigated on a single particle basis using a quantitative energy-dispersive electron probe X-ray microanalysis, suggesting the different sources and formation mechanisms of secondary aerosols, i.e., the predominant presence of sulfate at the ATTO site from mostly biogenic emissions and the elevated influences of nitrates from anthropogenic activities at the Manaus site.
Aerosol samples collected at a remote site in the Amazonian rainforest (ATTO) and an urban site...
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