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Volume 17, issue 12 | Copyright

Special issue: Pan-Eurasian Experiment (PEEX)

Atmos. Chem. Phys., 17, 7965-7975, 2017
https://doi.org/10.5194/acp-17-7965-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 30 Jun 2017

Research article | 30 Jun 2017

Size distribution and source of black carbon aerosol in urban Beijing during winter haze episodes

Yunfei Wu1, Xiaojia Wang1, Jun Tao2, Rujin Huang3, Ping Tian4, Junji Cao3, Leiming Zhang5, Kin-Fai Ho6, Zhiwei Han1, and Renjian Zhang1 Yunfei Wu et al.
  • 1CAS Key Laboratory of Regional Climate-Environment for Temperate East Asia, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
  • 2South China Institute of Environmental Sciences, Ministry of Environmental Protection, Guangzhou, China
  • 3CAS Key Laboratory of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China
  • 4Beijing Weather Modification Office, Beijing, China
  • 5Air Quality Research Division, Science and Technology Branch, Environment and Climate Change Canada, Toronto, Canada
  • 6The Jockey Club School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, China

Abstract. Black carbon (BC) has important impact on climate and environment due to its light absorption ability, which greatly depends on its physicochemical properties including morphology, size and mixing state. The size distribution of the refractory BC (rBC) was investigated in urban Beijing in the late winter of 2014, during which there were frequent haze events, through analysis of measurements obtained using a single-particle soot photometer (SP2). By assuming void-free rBC with a density of 1.8gcm−3, the mass of the rBC showed an approximately lognormal distribution as a function of the volume-equivalent diameter (VED), with a peak diameter of 213nm. Larger VED values of the rBC were observed during polluted periods than on clean days, implying an alteration in the rBC sources, as the size distribution of the rBC from a certain source was relative stable, and VED of an individual rBC varied little once it was emitted into the atmosphere. The potential source contribution function analysis showed that air masses from the south to east of the observation site brought higher rBC loadings with more thick coatings and larger core sizes. The mean VED of the rBC presented a significant linear correlation with the number fraction of thickly coated rBC, extrapolating to be  ∼150nm for the completely non-coated or thinly coated rBC. It was considered as the typical mean VED of the rBC from local traffic sources in this study. Local traffic was estimated to contribute 35 to 100% of the hourly rBC mass concentration with a mean of 59% during the campaign. Lower local traffic contributions were observed during polluted periods, suggesting increasing contributions from other sources (e.g., coal combustion and biomass burning) to the rBC. Thus, the heavy pollution in Beijing was greatly influenced by other sources in addition to the local traffic.

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As black carbon (BC) aerosols play an important role in the climate and environment, the size distribution of refractory BC (rBC) was investigated. On this basis, the source of rBC was further analyzed. The local traffic exhausts contributed greatly to the rBC in urban areas. However, its contribution decreased significantly in the polluted period compared to the clean period, implying the increasing contribution of other sources, e.g., coal combustion or biomass burning, in the polluted period.
As black carbon (BC) aerosols play an important role in the climate and environment, the size...
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