Origin of water-soluble organic aerosols at the Maïdo high-altitude observatory, Réunion Island, in the tropical Indian Ocean

<p>The tropical and subtropical Indian Ocean (IO) is expected to be a significant source of water-soluble organic aerosols (WSOAs), which are important factors relevant to cloud formation of aerosol particles. Current atmospheric numerical models significantly underestimate the budget of organ...

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Autores principales: S. A. Simu, Y. Miyazaki, E. Tachibana, H. Finkenzeller, J. Brioude, A. Colomb, O. Magand, B. Verreyken, S. Evan, R. Volkamer, T. Stavrakou
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Publicado: Copernicus Publications 2021
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spelling oai:doaj.org-article:f5a0066c985847a0a335f0817462900e2021-11-24T11:01:13ZOrigin of water-soluble organic aerosols at the Maïdo high-altitude observatory, Réunion Island, in the tropical Indian Ocean10.5194/acp-21-17017-20211680-73161680-7324https://doaj.org/article/f5a0066c985847a0a335f0817462900e2021-11-01T00:00:00Zhttps://acp.copernicus.org/articles/21/17017/2021/acp-21-17017-2021.pdfhttps://doaj.org/toc/1680-7316https://doaj.org/toc/1680-7324<p>The tropical and subtropical Indian Ocean (IO) is expected to be a significant source of water-soluble organic aerosols (WSOAs), which are important factors relevant to cloud formation of aerosol particles. Current atmospheric numerical models significantly underestimate the budget of organic aerosols and their precursors, especially over tropical oceans. This is primarily due to poor knowledge of sources and the paucity of observations of these parameters considering spatial and temporal variation over the tropical open ocean. To evaluate the contribution of sources to WSOA as well as their formation processes, submicrometer aerosol sampling was conducted at the high-altitude Maïdo observatory (21.1<span class="inline-formula"><sup>∘</sup></span> S, 55.4<span class="inline-formula"><sup>∘</sup></span> E; 2160 m a.s.l.), located on the remote island of La Réunion in the southwest IO. The aerosol samples were continuously collected during local daytime and nighttime, which corresponded to the ambient conditions of the marine boundary layer (MBL) and free troposphere (FT), respectively, from 15 March to 24 May 2018. Chemical analysis showed that organic matter was the dominant component of submicrometer water-soluble aerosol (<span class="inline-formula">∼</span> 45 <span class="inline-formula">±</span> 17 %) during the wet season (15 March–23 April). On the other hand, sulfate dominated (<span class="inline-formula">∼</span> 77 <span class="inline-formula">±</span> 17 %) during the dry season (24 April–24 May), most of which was attributable to the effect of volcanic eruption. Measurements of the stable carbon isotope ratio of water-soluble organic carbon (WSOC) suggested that marine sources contributed significantly to the observed WSOC mass in both the MBL and the FT in the wet season, whereas a mixture of marine and terrestrial sources contributed to WSOC in the dry season. The distinct seasonal changes in the dominant source of WSOC were also supported by Lagrangian trajectory analysis. Positive matrix factorization analysis suggested that marine secondary organic aerosol (OA) dominantly contributed to the observed WSOC mass (<span class="inline-formula">∼</span> 70 %) during the wet season, whereas mixtures of marine and terrestrial sources contributed during the dry season in both MBL and FT. Overall, this study demonstrates that the effect of marine secondary sources is likely important up to the FT in the wet season, which may affect cloud formation as well as direct radiative forcing over oceanic regions.</p>S. A. SimuS. A. SimuY. MiyazakiE. TachibanaH. FinkenzellerH. FinkenzellerJ. BrioudeA. ColombO. MagandB. VerreykenB. VerreykenB. VerreykenS. EvanR. VolkamerR. VolkamerT. StavrakouCopernicus PublicationsarticlePhysicsQC1-999ChemistryQD1-999ENAtmospheric Chemistry and Physics, Vol 21, Pp 17017-17029 (2021)
institution DOAJ
collection DOAJ
language EN
topic Physics
QC1-999
Chemistry
QD1-999
spellingShingle Physics
QC1-999
Chemistry
QD1-999
S. A. Simu
S. A. Simu
Y. Miyazaki
E. Tachibana
H. Finkenzeller
H. Finkenzeller
J. Brioude
A. Colomb
O. Magand
B. Verreyken
B. Verreyken
B. Verreyken
S. Evan
R. Volkamer
R. Volkamer
T. Stavrakou
Origin of water-soluble organic aerosols at the Maïdo high-altitude observatory, Réunion Island, in the tropical Indian Ocean
description <p>The tropical and subtropical Indian Ocean (IO) is expected to be a significant source of water-soluble organic aerosols (WSOAs), which are important factors relevant to cloud formation of aerosol particles. Current atmospheric numerical models significantly underestimate the budget of organic aerosols and their precursors, especially over tropical oceans. This is primarily due to poor knowledge of sources and the paucity of observations of these parameters considering spatial and temporal variation over the tropical open ocean. To evaluate the contribution of sources to WSOA as well as their formation processes, submicrometer aerosol sampling was conducted at the high-altitude Maïdo observatory (21.1<span class="inline-formula"><sup>∘</sup></span> S, 55.4<span class="inline-formula"><sup>∘</sup></span> E; 2160 m a.s.l.), located on the remote island of La Réunion in the southwest IO. The aerosol samples were continuously collected during local daytime and nighttime, which corresponded to the ambient conditions of the marine boundary layer (MBL) and free troposphere (FT), respectively, from 15 March to 24 May 2018. Chemical analysis showed that organic matter was the dominant component of submicrometer water-soluble aerosol (<span class="inline-formula">∼</span> 45 <span class="inline-formula">±</span> 17 %) during the wet season (15 March–23 April). On the other hand, sulfate dominated (<span class="inline-formula">∼</span> 77 <span class="inline-formula">±</span> 17 %) during the dry season (24 April–24 May), most of which was attributable to the effect of volcanic eruption. Measurements of the stable carbon isotope ratio of water-soluble organic carbon (WSOC) suggested that marine sources contributed significantly to the observed WSOC mass in both the MBL and the FT in the wet season, whereas a mixture of marine and terrestrial sources contributed to WSOC in the dry season. The distinct seasonal changes in the dominant source of WSOC were also supported by Lagrangian trajectory analysis. Positive matrix factorization analysis suggested that marine secondary organic aerosol (OA) dominantly contributed to the observed WSOC mass (<span class="inline-formula">∼</span> 70 %) during the wet season, whereas mixtures of marine and terrestrial sources contributed during the dry season in both MBL and FT. Overall, this study demonstrates that the effect of marine secondary sources is likely important up to the FT in the wet season, which may affect cloud formation as well as direct radiative forcing over oceanic regions.</p>
format article
author S. A. Simu
S. A. Simu
Y. Miyazaki
E. Tachibana
H. Finkenzeller
H. Finkenzeller
J. Brioude
A. Colomb
O. Magand
B. Verreyken
B. Verreyken
B. Verreyken
S. Evan
R. Volkamer
R. Volkamer
T. Stavrakou
author_facet S. A. Simu
S. A. Simu
Y. Miyazaki
E. Tachibana
H. Finkenzeller
H. Finkenzeller
J. Brioude
A. Colomb
O. Magand
B. Verreyken
B. Verreyken
B. Verreyken
S. Evan
R. Volkamer
R. Volkamer
T. Stavrakou
author_sort S. A. Simu
title Origin of water-soluble organic aerosols at the Maïdo high-altitude observatory, Réunion Island, in the tropical Indian Ocean
title_short Origin of water-soluble organic aerosols at the Maïdo high-altitude observatory, Réunion Island, in the tropical Indian Ocean
title_full Origin of water-soluble organic aerosols at the Maïdo high-altitude observatory, Réunion Island, in the tropical Indian Ocean
title_fullStr Origin of water-soluble organic aerosols at the Maïdo high-altitude observatory, Réunion Island, in the tropical Indian Ocean
title_full_unstemmed Origin of water-soluble organic aerosols at the Maïdo high-altitude observatory, Réunion Island, in the tropical Indian Ocean
title_sort origin of water-soluble organic aerosols at the maïdo high-altitude observatory, réunion island, in the tropical indian ocean
publisher Copernicus Publications
publishDate 2021
url https://doaj.org/article/f5a0066c985847a0a335f0817462900e
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