ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-11-21713-2011 Typical types and formation mechanisms of haze in an eastern Asia megacity, Shanghai Huang K. 1 2 Zhuang G. 1 Lin Y. 1 Fu J. S. 2 Wang Q. 1 Liu T. 1 Zhang R. 1 Jiang Y. 1 Deng C. 1 Center for Atmospheric Chemistry Study, Department of Environmental Science and Engineering, Fudan University, Shanghai, 200433, China Department of Civil and Environmental Engineering, The University of Tennessee, Knoxville, TN 37996, USA 02 08 2011 11 8 21713 21767 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/11/21713/2011/acpd-11-21713-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/11/21713/2011/acpd-11-21713-2011.pdf

An intensive aerosol and gases campaign has been performed at Shanghai in the Yangtze River Delta region over Eastern China from late March to early June 2009. This study provided a complementary picture of typical haze types and formation mechanisms in megacities over China by using a synergy of ground-based monitoring, satellite observation and lidar inversion. During the whole study period, several extreme low visibility periods were observed with distinct characteristics, and three typical haze types were identified, i.e. secondary inorganic pollution, dust, and biomass burning. Sulfate, nitrate and ammonium accounted for a major part of PM<sub>2.5</sub> mass during the secondary inorganic pollution, and the good correlation between SO<sub>2</sub>/NO<sub>x</sub>/CO and PM<sub>2.5</sub> indicated that coal burning and vehicle emission were the major sources. Large-scale regions with high AOD and low Ångström exponent were detected by remote-sensing observation during the dust pollution episode, and this episode corresponded to coarse particles rich in mineral components such as Al and Ca with mineral aerosol contributing 76.8 % to TSP. The relatively low Ca/Al ratio of 0.75 combined with the air mass backward trajectory analysis suggested the dust source from Gobi Desert. Typical tracers for biomass burning from satellite observation (column CO and HCHO) and from ground measurement (CO, particulate K<sup>+</sup>, OC, and EC) were greatly enhanced during the biomass burning pollution episode. The exclusive linear correlation between CO and PM<sub>2.5</sub> corroborated that organic aerosol dominated aerosol chemistry during biomass burning, and the high concentration and enrichment degree of arsenic (As) could be also partly derived from biomass burning. Aerosol optical profile observed by lidar demonstrated that aerosol was mainly constrained below the boundary layer and comprised of spheric aerosol (depolarization ratio <5 %) during the secondary inorganic and biomass burning episodes, while during the dust episode thick dust layer distributed at altitudes from near the ground to 1.4 km (average depolarization ratio = 0.122 ± 0.023) with dust accounting for 44–55 % of the total aerosol extinction coefficient. This study had illustrated a good picture of the typical haze types and proposed that identification of the complicated emission sources was important for the air quality improvement in megacities in China.

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