Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2016-976
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
16 Jan 2017
Review status
A revision of this discussion paper was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
Real-Time Aerosol Optical Properties, Morphology and Mixing States under Clear, Haze and Fog Episodes in the Summer of Urban Beijing
Rui Li1, Yunjie Hu1, Ling Li1, Hongbo Fu1,2, and Jianmin Chen1 1Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science & Engineering, Fudan University, Shanghai 200433, China Chinese Academy of Sciences, Institute of Atmosphere Physics, Beijing 100029
2Collaborative Innovation Center of Atmospheric Environment and Equipment Technology (CICAEET), Nanjing University of Information Science and Technology, Nanjing 210044, China
Abstract. Characteristics of aerosol optical properties, morphologies and their relationship were studied in urban Beijing during the clear, haze and fog episodes, sampled from 24th May to 22nd Jun, 2012. Transmission Electron Microscope (TEM), a Cavity Ring Down Spectrometer (CRDS), a nephelometer and an aethalometer were employed to investigate the corresponding changes of the aerosol properties. Five episodes were categorised according to the meteorological conditions, composition and optical variation. Results show the clear episode (EP-2 and EP-4) featured as the low light extinction with less pollutants, which are mostly externally mixed. Coarse particles were scarcely observed in EP-2 due to the washout of a previous heavy rain. Thus the size distribution in EP-2 was smaller than EP-4, which had some mineral particles introduced from the north. In contrast, industry-induced haze (EP-1) and biomass burning-induced haze (EP-5) were both impacted by the south air mass. Higher AOD (Aerosol Optical Depth) values illustrated heavy loading particle concentrations. Due to the collision, size of most particles was larger with the diameter of 1 μm, resulting in a higher scattering coefficient. However, as the influence of severe crop residue combustion, a large fraction of soot was detected, which sticks to the KCl transformed sulphate or nitrate particles. The light absorption enhancement was contributed by both Black Carbon (BC) acceleration and other light absorbing substances. Comparatively, soot fog period detected in EP-3 was mostly internally mixed with sulphates and nitrates, which revealed themselves after electron exposure. The larger size distribution was likely to be caused by both hygroscopic growth and collision. More internally mixed particles were observed, which favored the light absorption. The comparison of all the episodes provides a deeper insight of how mixing states influence the aerosol extinction properties and also a clue to the air pollution control in the crop burning seasons.

Citation: Li, R., Hu, Y., Li, L., Fu, H., and Chen, J.: Real-Time Aerosol Optical Properties, Morphology and Mixing States under Clear, Haze and Fog Episodes in the Summer of Urban Beijing, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-976, in review, 2017.
Rui Li et al.
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version      Supplement - Supplement
 
RC1: 'Minor revisions needed', Anonymous Referee #1, 23 Jan 2017 Printer-friendly Version Supplement 
AC1: 'Real-Time Aerosol Optical Properties, Morphology and Mixing States under Clear, Haze and Fog Episodes in the summer of Urban Beijing', Hongbo Fu, 19 Feb 2017 Printer-friendly Version 
AC2: 'Real-Time Aerosol Optical Properties, Morphology and Mixing States under Clear, Haze and Fog Episodes in the summer of Urban Beijing', Hongbo Fu, 19 Feb 2017 Printer-friendly Version 
AC4: 'Real-Time Aerosol Optical Properties, Morphology and Mixing States under Clear, Haze and Fog Episodes in the summer of Urban Beijing', Hongbo Fu, 19 Feb 2017 Printer-friendly Version Supplement 
 
RC2: 'Comment on “Real-Time Aerosol Optical Properties, Morphology and Mixing States under Clear, Haze and Fog Episodes in the Summer of Urban Beijing” by Rui Li et al.', Anonymous Referee #2, 16 Feb 2017 Printer-friendly Version 
AC3: 'Real-Time Aerosol Optical Properties, Morphology and Mixing States under Clear, Haze and Fog Episodes in the summer of Urban Beijing', Hongbo Fu, 19 Feb 2017 Printer-friendly Version Supplement 
 
RC3: 'comments on acp-2016-308', Anonymous Referee #3, 18 Feb 2017 Printer-friendly Version 
 
AC5: 'Real-Time Aerosol Optical Properties, Morphology and Mixing States under Clear, Haze and Fog Episodes in the summer of Urban Beijing', Hongbo Fu, 06 Mar 2017 Printer-friendly Version Supplement 
 
AC6: 'Real-Time Aerosol Optical Properties, Morphology and Mixing States under Clear, Haze and Fog Episodes in the summer of Urban Beijing', Hongbo Fu, 06 Mar 2017 Printer-friendly Version 
 
AC7: 'Real-Time Aerosol Optical Properties, Morphology and Mixing States under Clear, Haze and Fog Episodes in the summer of Urban Beijing', Hongbo Fu, 06 Mar 2017 Printer-friendly Version Supplement 
Rui Li et al.
Rui Li et al.

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Short summary
The clear episode (EP-2 and EP-4) featured as the low light extinction with less pollutants, which are mostly externally mixed. The size distribution in EP-2 was smaller than EP-4, which had some mineral particles from the north. In contrast, industry-induced haze (EP-1) and biomass burning-induced haze (EP-5) were both impacted by the south air mass. Soot fog period detected in EP-3 was mostly internally mixed with sulphates and nitrates.
The clear episode (EP-2 and EP-4) featured as the low light extinction with less pollutants,...
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