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"APEC Blue": Secondary Aerosol Reductions from Emission Controls in Beijing

Research output: Contribution to Journal/MagazineJournal articlepeer-review

  • Yele Sun
  • Zifa Wang
  • Oliver Wild
  • Weiqi Xu
  • Chen Chen
  • Pingqing Fu
  • Wei Du
  • Libo Zhou
  • Qi Zhang
  • Tingting Han
  • Qingqing Wang
  • Xiaole Pan
  • Haitao Zheng
  • Jie Li
  • Xiaofeng Guo
  • Jianguo Liu
  • Douglas R. Worsnop
Article number20668
<mark>Journal publication date</mark>18/02/2016
<mark>Journal</mark>Scientific Reports
Number of pages9
Publication StatusPublished
<mark>Original language</mark>English


China implemented strict emission control measures in Beijing and surrounding regions to ensure good air quality during the 2014 Asia-Pacific Economic Cooperation (APEC) summit. We conducted synchronous aerosol particle measurements with two aerosol mass spectrometers at different heights on a meteorological tower in urban Beijing to investigate the variations in particulate composition, sources and size distributions in response to emission controls. Our results show consistently large reductions in secondary inorganic aerosol (SIA) of 61-67% and 51-57%, and in secondary organic aerosol (SOA) of 55% and 37%, at 260 m and ground level, respectively, during the APEC summit. These changes were mainly caused by large reductions in accumulation mode particles and by suppression of the growth of SIA and SOA by a factor of 2-3, which led to blue sky days during APEC commonly referred to as "APEC Blue". We propose a conceptual framework for the evolution of primary and secondary species and highlight the importance of regional atmospheric transport in the formation of severe pollution episodes in Beijing. Our results indicate that reducing the precursors of secondary aerosol over regional scales is crucial and effective in suppressing the formation of secondary particulates and mitigating PM pollution.