Organic Molecular Compositions and Size Distributions of Chinese Summer and Autumn Aerosols from Nanjing: Characteristic Haze Event Caused by Wheat Straw Burning

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• 作者：Gehui Wang ; Kimitaka Kawamura ; Mingjie Xie ; Shuyuan Hu ; Junji Cao ; Zhisheng An ; John G. Waston ; Judith C. Chow
• 刊名：Environmental Science & Technology
• 出版年：2009
• 出版时间：September 1, 2009
• 年：2009
• 卷：43
• 期：17
• 页码：6493-6499
• 全文大小：311K
• 年卷期：v.43,no.17(September 1, 2009)
• ISSN：1520-5851

文摘

Size-segregated aerosol samples were collected in urban Nanjing, China during summer and autumn of 2007 including a period of hazy days during June 1−5. Organic aerosols in the haze event were characterized by elevated concentrations of levoglucosan, high molecular weight (HMW) n-alkanes, and HMW fatty acids due to the emissions from field burning of wheat straw. In contrast, organic aerosols on nonhazy days were characterized by a predominance of fossil fuel combustion products. Levoglucosan (4030 ng m⁻³), n-alkanes (1520 ng m⁻³), fatty acids (2629 ng m⁻³), and PAHs (57 ng m⁻³) in the haze samples were 3−40 times more abundant than those in nonevent samples. Approximately 30−90% of the organics during the haze period can be attributed to wheat straw burning. Concentrations of particulate material (PM) mass, n-alkanes, and low molecular weight (LMW) PAHs showed a unimodal size distribution, peaking at 0.7−1.1 μm during the hazy days, and a bimodal distribution, peaking at 0.7−1.1 μm and 4.7−5.8 μm during nonhazy days. The geometric mean diameters (GMDs) of organic aerosols are larger in the fine mode (<2.1 μm) during the hazy days, suggesting aerosols emitted from the wheat straw burning are larger than those from fossil fuel combustion, and fine particle coagulation and organic compound repartitioning were enhanced.