Abstract
Photochemical smog, characterized by high concentrations of ozone (O3) and fine particles (PM2.5) in the atmosphere, has become one of the top environmental concerns in China. Volatile organic compounds (VOCs), one of the key precursors of O3 and secondary organic aerosol (SOA) (an important component of PM2.5), have a critical influence on atmospheric chemistry and subsequently affect regional and global climate. Thus, VOCs have been extensively studied in many cities and regions in China, especially in the North China Plain, the Yangtze River Delta and the Pearl River Delta regions where photochemical smog pollution has become increasingly worse over recent decades. This paper reviews the main studies conducted in China on the characteristics and sources of VOCs, their relationship with O3 and SOA, and their removal technology. This paper also provides an integrated literature review on the formulation and implementation of effective control strategies of VOCs and photochemical smog, as well as suggestions for future directions of VOCs study in China.
Highlights
With rapid industrialization and urbanization in China, air pollution associated with photochemical smog and haze-fog, characterized by high levels of ozone (O3) and fine particulates (PM2.5), has become one of the most severe environmental pollution issues in many cities and regions of China (Zhang et al, 2008a, 2008b; Guo et al, 2009, 2013; Wang and Hao, 2012; Huang et al, 2014; Lee, 2015)
Based on data collected at air monitoring stations in 74 cities throughout China, it was found that the annual average concentration of PM2.5 exceeded the national ambient air quality standard of 35 μg/m3 in 71 cities, with the highest average value of 115 μg/m3 (Liu et al, 2013a)
The results indicated that combustion activities, solvent usage and biogenic emissions were the main sources of non-methane hydrocarbons (NMHCs), while vehicle emissions, cooking and biogenic sources mainly contributed to the carbonyls
Summary
With rapid industrialization and urbanization in China, air pollution associated with photochemical smog and haze-fog, characterized by high levels of ozone (O3) and fine particulates (PM2.5), has become one of the most severe environmental pollution issues in many cities and regions of China (Zhang et al, 2008a, 2008b; Guo et al, 2009, 2013; Wang and Hao, 2012; Huang et al, 2014; Lee, 2015). Controlling VOCs emissions can be helpful to alleviate photochemical smog in cities and regions in China, especially because the production of O3 in urban areas is usually limited by VOCs and because the loadings of SOA in PM2.5 have become more significant in recent years (Huang et al, 2014; Cheng et al, 2010a, 2010b; Zhang et al, 2008a; Xu et al, 2008a, 2008b). To develop scientifically sound and effective control strategies on photochemical air pollution, a great deal of research sponsored by the Chinese central government and some local governments has been/is being conducted to investigate the characteristics of VOCs, including their abundances and sources, their roles in photochemical O3 and SOA formation, and VOCs removal technology in different areas.
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