[1] Using a CIMEL Sun photometer, we conducted continuous observations over the urban area of Shanghai (31 14′N, 121 32′E) from 18 April 2007 to 31 January 2009. The aerosol optical depth (AOD), Angstrom wavelength exponent, single scattering albedo (w 0 ), and aerosol particle size distribution were derived from the observational data. The monthly mean AOD reached a maximum value of 1.20 in June and a minimum value of 0.43 in January. The monthly averaged Angstrom wavelength exponent reached a minimum value of 1.15 in April and a maximum value of 1.41 in October. The frequencies of the AOD and Angstrom wavelength exponent presented lognormal distributions. The averaged w 0 at 550 nm was 0.94 throughout the observation period, indicating that the aerosols over Shanghai are composed mainly of scattering particles. The concentrations of coarse mode and accumulation mode aerosols over Shanghai were highest in spring compared with other seasons, especially for those particles with radii between 1.0 and 2.0 mm. The median radius of monthly averaged accumulation mode aerosols increased with increasing AOD, and fine particles accounted for the majority of the aerosol volume concentration. The ratios of the monthly averaged volume concentration of accumulation mode and coarse mode aerosols (V f /V c ) were over 0.6 for all months studied and reached up to 1.94 in August. The volumes of the two modes changed with AOD, but their correlations presented different sensitivities, that is, the volume concentration of accumulation mode aerosols was more sensitive to variations in AOD than that of coarse mode aerosols. The aerosol volume concentration decreased with increasing w 0 , indicating that the higher the volume concentration of aerosols, the higher the absorption in particle extinction properties. The increase in absorption was caused primarily by secondary species coated on black carbon (BC) and primary organic carbon (POC) particles.Citation: He, Q
[1] Heavy haze frequently occurs in winter over a coal-burning region, the Taiyuan Basin, in the eastern China Loess Plateau, which is the upstream area of the North China Plain. We participated in three research flights to collect aerosol particles and to monitor SO 2 concentration in hazes from the ground (780 m asl) up to $4000 m during 17-18 December, 2010. Meteorological records reveal that the whole haze column (ground to 4000 m) was stable and could be further divided into three sub-layers depending on the sampling altitude, which are characterized by two shifts of the lapse rate of virtual potential temperature and water vapor mixing ratio: Layer-1, surface to 1500 m; Layer-2, 1500 $ 3000 m on 17 December, and 1500 $ 2500 m on 18 December; Layer-3, above 3000 m on 17 December and above 2500 m on 18 December. SO 2 concentration was 16-116 ppb with an average of 58 ppb in the Layer-1, 2-45 ppb with an average of 10 ppb in the Layer-2, and 1-10 ppb with an average of 4 ppb in the Layer-3. The accumulation of SO 2 in the Layer-1 was due to the stable meteorological conditions and the strong anthropogenic emissions in addition to the possible valley topography. Analyses of the collected particles using a transmission electron microscope revealed the dominance of organic particles and fly ash in the Layer-1 and Layer-2 and sulfate particles in the Layer-3. The organic aerosols frequently contained certain amounts of Si and Cl. Fly ash particles consisted of O and Si with minor Fe, Mn, Zn, Ti, Pb, As, Co, and Cr. These two types of aerosol particles are typically emitted from coal burning. These results indicate that the haze particles were characterized in principle by aerosols from primary emissions of coal burning, which are different from those over the North China Plain where secondary sulfate particles are the dominant component.
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