Molecular Characteristics of Urban Organic Aerosols from Nanjing: A Case Study of A Mega-City in China

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• 作者：Gehui Wang and Kimitaka Kawamura
• 刊名：Environmental Science & Technology
• 出版年：2005
• 出版时间：October 1, 2005
• 年：2005
• 卷：39
• 期：19
• 页码：7430 - 7438
• 全文大小：197K
• 年卷期：v.39,no.19(October 1, 2005)
• ISSN：1520-5851

文摘

Over 90 organic species have been determined in fineaerosols (PM_2.5) collected during the summer and winterin Nanjing, a typical mega-city in China, using gaschromatography-mass spectrometry. The organic compounds detected were apportioned to four emission sources(i.e., plant emission, fossil fuel combustion, biomassburning, and soil resuspension) and secondary oxidationproducts. The most abundant classes of compounds are fattyacids, followed by sugars, dicarboxylic acids excludingoxalic and malonic acids, and n-alkanes, while alcohols,polyols/polyacids and lignin/sterols are less abundant. Totalamounts of the seven classes of compounds were onaverage 938 ng m^-3 in the summer and 1301 ng m^-3 inthe winter, respectively, contributing 0.26-1.96% of particlemass (PM_2.5). In the summer, n-alkanes were heavilyenhanced by vegetation emissions with a maximum carbonnumber (C_max) at C₂₉, whereas they were dominated byemissions from fossil fuels combustion with a C_max at C₂₂/C₂₃ in the winter. Concentrations of unsaturated fattyacids were lower in the summer than in the winter, beingconsistent with enhanced photooxidation of unsaturatedfatty acids in the summer. Concentrations of dicarboxylicacids for the summer aerosols were much higher inthe daytime than in the nighttime, indicating increasedphotochemical production in the daytime. In the summer,plant emissions were the most significant source of organicaerosols, contributing more than 33% of total compoundmass (TCM), followed by fossil fuel combustion or secondaryoxidation. In contrast, fossil fuel combustion was thedominant source of winter organic aerosols, contributingmore than 51% of TCM, followed by plant emissions andsecondary oxidation products. The quantitative resultson sugars and lignin pyrolysis products further suggestedthat biomass burning and soil resuspension are alsosignificant sources of urban organic aerosols.