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Molecular characterization of urban organic aerosol in tropical India: contributions of primary emissions and secondary photooxidation

by P. Q. Fu, K. Kawamura, C. M. Pavuluri, T. Swaminathan, J. Chen
Atmospheric Chemistry and Physics ()

Abstract

Org. mol. compn. of PM10 samples, collected at Chennai in tropical India, was studied using capillary gas chromatog./mass spectrometry. Fourteen org. compd. classes were detected in the aerosols, including aliph. lipids, sugar compds., lignin products, terpenoid biomarkers, sterols, arom. acids, hydroxy/polyacids, phthalate esters, hopanes, Polycyclic Arom. Hydrocarbons (PAHs), and photooxidn. products from biogenic Volatile Org. Compds. (VOCs). At daytime, phthalate esters were found to be the most abundant compd. class; however, at nighttime, fatty acids were the dominant one. Di-(2-ethylhexyl) phthalate, C16 fatty acid, and levoglucosan were identified as the most abundant single compds. The nighttime maxima of most orgs. in the aerosols indicate a land/sea breeze effect in tropical India, although some other factors such as local emissions and long-range transport may also influence the compn. of org. aerosols. However, biogenic VOC oxidn. products (e.g., 2-methyltetrols, pinic acid, 3-hydroxyglutaric acid and ╬▓-caryophyllinic acid) showed diurnal patterns with daytime maxima. Interestingly, terephthalic acid was maximized at nighttime, which is different from those of phthalic and isophthalic acids. A pos. relation was found between 1,3,5-triphenylbenzene (a tracer for plastic burning) and terephthalic acid, suggesting that the field burning of municipal solid wastes including plastics is a significant source of terephthalic acid. Org. compds. were further categorized into several groups to clarify their sources. Fossil fuel combustion (24-43%) was recognized as the most significant source for the total identified compds., followed by plastic emission (16-33%), secondary oxidn. (8.6-23%), and microbial/marine sources (7.2-17%). In contrast, the contributions of terrestrial plant waxes (5.9-11%) and biomass burning (4.2-6.4%) were relatively small. This study demonstrates that, in addn. to fossil fuel combustion and biomass burning, the open-burning of plastics in urban area also contributes to the org. aerosols in South Asia. [on SciFinder(R)]

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