Abstract
Abstract. The emission of pollutants is extremely reduced during the annual Chinese Spring Festival (SF) in Shenzhen, China. During the SF, traffic flow drops by ∼ 50 % and the industrial plants are almost entirely shut down in Shenzhen. To characterize the variation in ambient air pollutants due to the Spring Festival effect, various gaseous and particulate pollutants were measured in real time in urban Shenzhen over three consecutive winters (2014–2016). The results indicate that the concentrations of NOx, volatile organic compounds (VOCs), black carbon (BC), primary organic aerosols, chloride, and nitrate in submicron aerosols decrease by 50–80 % during SF periods relative to non-Spring Festival periods, regardless of meteorological conditions. This decrease suggests that these pollutants are mostly emitted or secondarily formed from urban local emissions. The concentration variation in species mostly from regional or natural sources, however, is found to be much less, such as for bulk fine particulate matter (PM2. 5). More detailed analysis of the Spring Festival effect reveals an urgent need to reduce emissions of SO2 and VOCs on a regional scale rather than on an urban scale to reduce urban PM2. 5 in Shenzhen, which can also be useful as a reference for other megacities in China.
Highlights
Most fragments of m/z 44 are the tracer of oxygenated organic aerosol and most fragments of m/z 57 are the tracer of primary hydrocarbon organic aerosol (Zhang et al, 2005), which are measured by aerosol mass spectrometer (AMS)
We can divide these air pollutants into three groups based on their percent changes: the group with the largest concentration drop includes the aromatics (−50 to −88 % for the various species; see Fig. S6), oxygenated VOCs (OVOCs) (−40 to −85 % for the various species; see Fig. S6), nitrogen oxide (NOx), chloride (Chl), nitrate (NO−3 ), black carbon (BC), and m/z 57
The significant decline in the ambient concentrations of NO−3 and Chl during the Spring Festival (SF) period indicates that their precursors have local origins, similar to the case for primary pollutants
Summary
The rapid economic development and urbanization of China over recent decades has brought with it the consequence of severe atmospheric pollution, especially in the key economically developed regions such as the Beijing–Tianjin–Hebei region (Sun et al, 2013, 2015; Guo et al, 2014), the Yangtze River Delta (Huang et al, 2013), and the Pearl River Delta (PRD), as well as their densely populated megacities (Hagler et al, 2006; Zhang et al, 2008; He et al, 2011). To explore the causes of urban air pollution in China, previous studies have focused on monitoring and comparing the reduction in emissions during special events, such as the 2008 Beijing Olympic Games (Huang et al, 2010), the 2010 Guangzhou Asian Games (Xu et al, 2013), the 2014 Asia Pacific Economic Cooperation conference (APEC) (Chen et al, 2015; Sun et al, 2016; Zhang et al, 2016), and the 2015 China Victory Day parade (Zhao et al, 2017) During such events, the air quality improved remarkably because of short-term limitations on traffic and industrial activity (Huang et al, 2010; Wang et al, 2010; Xu et al, 2013; Sun et al, 2016; Zhao et al, 2017). During the weeklong holiday (in January or February every year), the urban emission patterns depart significantly from the usual pat-
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