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Organic and inorganic markers and stable C-, N-isotopic compositions of tropical coastal aerosols from megacity Mumbai: sources of organic aerosols and atmospheric processing

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Title Organic and inorganic markers and stable C-, N-isotopic compositions of tropical coastal aerosols from megacity Mumbai: sources of organic aerosols and atmospheric processing
 
Creator AGGARWAL, SG
KAWAMURA, K
UMARJI, GS
TACHIBANA, E
PATIL, RS
GUPTA, PK
 
Subject NORTHERN JAPAN IMPLICATION
INDIAN-OCEAN EXPERIMENT
DICARBOXYLIC-ACIDS
KETOCARBOXYLIC ACIDS
MASS-SPECTROMETRY
ALPHA-DICARBONYLS
SOUTHEAST-ASIA
EAST-ASIA
CARBON
NITROGEN
 
Description 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 (C-2), azelaic acid (C-9), and levoglucosan. The results revealed that biofuel/biomass burning and fossil fuel combustion are the major sources of the Mumbai aerosols. Nitrogen-isotopic (delta N-15) 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, C-2 diacid and nssSO(4)(2-), do not show diurnal changes. Concentrations of C-2 diacid and WSOC show a strong correlation (r(2) = 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 C-9 diacid present a positive correlation (r(2) = 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 (delta C-13) 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 delta C-13 values suggested that the relative increment in C-13 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.
 
Publisher COPERNICUS GESELLSCHAFT MBH
 
Date 2014-10-17T05:57:16Z
2014-10-17T05:57:16Z
2013
 
Type Article
 
Identifier ATMOSPHERIC CHEMISTRY AND PHYSICS, 13(9)4667-4680
1680-7316
1680-7324
http://dx.doi.org/10.5194/acp-13-4667-2013
http://dspace.library.iitb.ac.in/jspui/handle/100/16124
 
Language en