Characteristics of Haze Pollution Episodes and Analysis of a Typical Winter Haze Process in Shanghai

Abstract

One-year field campaign was conducted from July 2013 to August 2014 at the site of East China University of Science and Technology (ECUST) in urban Shanghai, and mass concentrations and chemical compositions of PM 2.5 were measured. Gaseous pollutants (SO 2 , NO 2 ) and meteorological parameters (wind speed, wind direction, pressure, temperature and relative humidity) were simultaneously obtained. In this study, PM 2.5 mass balances on haze and non-haze days were reconstructed and the sum of secondary inorganic aerosols (SIA) and organic matter (OM) accounted for over 80%. The fraction of nitrate in SIA was much higher on haze days than that on non-haze days, while the corresponding fraction of ammonium was lower, implying that the variations of the sources and formation processes of SIA on haze days. In theory, sulfate and nitrate might be almost fully neutralized by ammonium. Moreover, the sulfur oxidation ratio (SOR) values were much higher than the nitrogen oxidation ratio (NOR) values, indicating the greater oxidation capacity of SO 2 would occur. On haze days, the high NOR values could be explained by the relatively low temperature, the high NO 2 concentration and the potential dominant gas-phase reaction. As for secondary organic aerosol (SOA), the formation processes were usually associated with nitrate formation. In winter, haze pollution episodes occurred more frequently than those in other seasons, associated with the different features of wind speed, wind direction and 72-h backward trajectory. In addition, one case from 17 November 2013 to 4 January 2014 was selected to investigate the formation mechanism of haze pollution episodes. The key factors that affected the haze formation might be the local stable synoptic conditions including weak surface wind, surface temperature inversion and high relative humidity, the long-range transportations from the Northwest and the large amounts of emissions from local sources.

Formation and Evolution Mechanisms for Two Extreme Haze Episodes in the Yangtze River Delta Region of China During Winter 2016

“…The comparisons of model results with routine air quality measurements show that the model typically reproduces the spatial patterns of surface PM 2.5 and the locations of maximum PM 2.5 concentrations, although it tends to underestimate the observations in the North China Plain (NCP; Figure ). The model underestimation of PM 2.5 may be associated with the missing of secondary organic aerosol in the MOSAIC aerosol module, which was reported to be even of similar importance (44–71% of OM) to SNA (Huang, Zhang, et al, ) and contribute 16% to PM 2.5 (Zhao et al, ) on haze days in eastern China.…”

Improved Color Attenuation Prior for Single-Image Haze Removal

“…Not only does haze removal function properly in hazy, foggy, or misty weather, but it also is appropriate for removing the effect of yellow dust or dust storm on the captured image. Owing to rapid industrialization and urbanization yellow dust is a topical issue in Eastern Asian countries [28] and there is growing demand for a highly sophisticated visibility restoration algorithm.…”

Absorption properties and size distribution of aerosol particles during the fall season at an urban site of Gwangju, Korea

“…Stable air conditions such as low wind speed, high surface pressure, and low boundary layer lead to the formation of a low-hanging layer and the poor dispersion of air pollutants. Ambient fine particles (PM 2.5 ) consist of primary particles from incomplete combustion of fossil and biomass fuels, and secondary particles formed through homogeneous and heterogeneous oxidation processes of SO 2 , NO 2 , NH 3 , and volatile organic compounds (VOCs) from anthropogenic and natural emission sources [4][5][6]. Haze phenomena, mainly caused by PM 2.5 , have attracted much attention due to their adverse effect on air quality, public health, and visibility [7][8][9][10][11].…”

“…Haze phenomena, mainly caused by PM 2.5 , have attracted much attention due to their adverse effect on air quality, public health, and visibility [7][8][9][10][11]. These studies of haze aimed to investigate source identification, chemical characterization, and formation processes of PM 2.5 during haze pollution [5,6,[12][13][14][15].…”