Abstract
During the 2014 Asia-Pacific Economic Cooperation (APEC) Economic Leaders’ Meetings in Beijing, the Chinese government made significant efforts to clear Beijing’s sky. The emission control measures were very effective and the improved air quality during the APEC Meetings was called the “APEC Blue”. To monitor and estimate how these emission control measures affected air quality in Beijing and its five neighboring large cities (Tianjin, Shijiazhuang, Tangshan, Jinan, and Qingdao), we compared and analyzed the satellite-retrieved Aerosol Optical Thickness (AOT) products of the pre-APEC (18–31 October), APEC (1–11 November), and post-APEC periods (11–31 November) in 2002–2014 and daily PM2.5 measurements of the three periods in 2014 on the ground. Compared with the pre- and post-APEC periods, both ground and satellite observations indicated significantly reduced aerosol loading during the 2014 APEC period in Beijing and its surroundings, but with apparent spatial heterogeneity. For example, the peak value of PM2.5 in Beijing were around 100 µg∙m−3 during the APEC period, however, during the pre- and post-APEC periods, the peak values were up to 290 µg∙m−3. The following temporal correlation analysis of mean AOT values between Beijing and other five cities for the past thirteen years (2002–2014) indicated that the potential emission source regions strongly impacting air quality of Beijing were confined within central and southern Hebei as well as northern and southwestern Shandong, in correspondence with the spatial pattern of Digital Earth Model (DEM) of the study region. In addition to stringent emission control measures, back trajectory analysis indicated that the relatively favorable regional transport pattern might also have contributed to the “APEC Blue” in Beijing. These results suggest that the “APEC Blue” is a temporarily regional phenomenon; a long-term improvement of air quality in Beijing is still challenging and joint efforts of the whole region are needed.
Highlights
Air pollution episodes over China in recent years have become a top environmental and health concern for the Chinese public and government [1,2]
Both daily PM2.5 and Aerosol Optical Thickness (AOT) measurements can characterize the effects of emission control measures during the Asia-Pacific Economic Cooperation (APEC) period on the local air quality: for example, the peak values of PM2.5 in Beijing were around 100 μg∙m−3 during the APEC period; during the pre- and post-APEC
Qingdao had a similar phenomenon (Figure 5). These results suggest the effectiveness of stringent emission control measures during the 2014 Beijing APEC Meetings and the effects of regional transport on air quality on the Northern China Plain [3,18,19]
Summary
Air pollution episodes over China in recent years have become a top environmental and health concern for the Chinese public and government [1,2]. Starting on 1 November 2014 and lasting through the Meetings (11 November 2014), these emission control measures included closing thousands of coal-consuming factories around Beijing and its surroundings, imposing traffic restrictions on millions of private vehicles from driving on alternate days, banning governmental and commercial vehicles in large urban centers, closing government offices, agencies, and public schools in Beijing, and halting construction and demolition work [4,5,6]. These emission control measures were very effective.
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