10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Measurements and Analysis of Chemical Composition of Urban Aerosol during High Pollution Events at Guanzhong Plain, China
Junji Cao, LIU HUIKUN, Key Laboratory of Aerosol Chemistry and Physics, IEECAS
Abstract Number: 468 Working Group: Aerosol Chemistry
Abstract Aerosol pollution is a serious environmental problem which influencing air quality, regional and global climates, and human health. Aerosol (PM2.5) samples were collected at Guanzhong Plain, China with six sampling sites at different cities in the year scale from 2012 to 2014. All of the six sites exhibited highest organic carbon (OC) and elemental carbon (EC) values in winter and lowest values in summer. OC correlates well with EC indicating similar emission sources. The contributions of secondary species SO42-, NO3- and NH4+ in total ions were greatest, and the high concentrations in winter were mainly due to emissions from coal combustion and biomass burning. During autumn the haze days were severest in Xi’an city with similar tendency of PM2.5 variations, and it was proved that biomass burning may be the main emission source of the regional pollution. In winter pollution episodes, the pollution patterns in Guanzhong Plain were similar which was resulted from strong secondary reactions and coal burning.Source apportionment using a positive matrix factorization receptor model indicates that on average secondary aerosol was the main source of PM2.5 (39.3%), followed by coal burning (17.3%), motor vehicle/industrial emissions (15.7%), fugitive dust (14.9%), and biomass burning (12.8%). The online, in situ measurement airborne species, especially the chemical composition of non-refectory submicron aerosol, during a heavy haze-fog event, was analyzed in detailed.The formation of secondary sulfate and organic aerosol were observed during the event. The sulfur oxidation ratio (SOR), defined as sulfate/(SO2+sulfate) were mostly over 0.10, with a maximum of ~0.30, when relative humidity > 80%. The aging product of organic aerosol (OA) were also observed in the event. The wet scattering coefficient was influenced by secondary sulfate, in the form of (NH4)2SO4, with contribution of 48.9% of wet particulate phase scattering. Thus decreased the visibility dramatically with a minimum of 128m. The current WRF-Chem model study suggested the secondary sulfate formation was essential to the increasing of sulfate concentration. The formation of secondary species was a decisive reason to form severe haze after fog event.
Keywords: PM2.5, source appointment, chemical formation