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| Titel |
Organic and inorganic markers and stable C-, N-isotopic compositions of tropical coastal aerosols from megacity Mumbai: sources of organic aerosols and atmospheric processing |
| VerfasserIn |
S. G. Aggarwal, K. Kawamura, G. S. Umarji, E. Tachibana, R. S. Patil, P. K. Gupta |
| 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 ; 13, no. 9 ; Nr. 13, no. 9 (2013-05-06), S.4667-4680 |
| Datensatznummer |
250018633
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| Publikation (Nr.) |
 copernicus.org/acp-13-4667-2013.pdf |
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| Zusammenfassung |
| To better understand the sources of PM10 samples in Mumbai, India,
aerosol chemical composition, i.e., total carbon (TC), organic carbon (OC),
elemental carbon (EC), water-soluble organic carbon (WSOC), and inorganic
ions were studied together with specific markers such as methanesulfonate
(MSA), oxalic acid (C2), azelaic acid (C9), and levoglucosan. The
results revealed that biofuel/biomass burning and fossil fuel combustion are
the major sources of the Mumbai aerosols. Nitrogen-isotopic (δ15N) composition of aerosol total nitrogen, which ranged from 18.1 to
25.4‰, also suggests that biofuel/biomass burning is a
predominate source in both the summer and winter seasons. Aerosol mass
concentrations of major species increased 3–4 times in winter compared to
summer, indicating enhanced emission from these sources in the winter season.
Photochemical production tracers, C2 diacid and nssSO42−, do
not show diurnal changes. Concentrations of C2 diacid and WSOC show a
strong correlation (r2 = 0.95). In addition, WSOC to OC (or TC)
ratios remain almost constant for daytime (0.37 ± 0.06 (0.28 ± 0.04))
and nighttime (0.38 ± 0.07 (0.28 ± 0.06)), suggesting that mixing
of fresh secondary organic aerosols is not significant and the Mumbai
aerosols are photochemically well processed. Concentrations of MSA and
C9 diacid present a positive correlation (r2 = 0.75), indicating
a marine influence on Mumbai aerosols in addition to local/regional
influence. Backward air mass trajectory analyses further suggested that the
Mumbai aerosols are largely influenced by long-range continental and
regional transport. Stable C-isotopic ratios (δ13C) of TC
ranged from −27.0 to −25.4‰, with slightly lower average
(−26.5 ± 0.3‰) in summer than in winter
(−25.9 ± 0.3‰). Positive correlation between
WSOC/TC ratios and δ13C values suggested that the relative increment in
13C of wintertime TC may be caused by prolonged photochemical
processing of organic aerosols in this season. This study suggests that in
winter, the tropical aerosols are more aged due to longer residence time in
the atmosphere than in summer aerosols. However, these conclusions are based
on the analysis of a limited number of samples (n=25) and more information
on this topic may be needed from other similar coastal sites in future. |
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