UC Davis UC Davis Previously Published Works Title Tropospheric volatile organic compounds in China. Permalink https://escholarship.org/uc/item/4r81f073 Authors Guo, H Ling, ZH Cheng, HR et al. Publication Date 2017 DOI 10.1016/j.scitotenv.2016.09.116 License https://creativecommons.org/licenses/by/4.0/ 4.0 Peer reviewed eScholarship.org Powered by the California Digital Library University of California Science of the Total Environment 574 (2017) 1021–1043 Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv Tropospheric volatile organic compounds in China H. Guo a,⁎,Z.H.Lingb,H.R.Chengc, I.J. Simpson d,X.P.Lyua,X.M.Wange,M.Shaof,H.X.Lua, G. Ayoko g, Y.L. Zhang e,S.M.Saundersh,S.H.M.Lami,J.L.Wangj,D.R.Blaked a Air Quality Studies, Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hong Kong, China b School of Atmospheric Sciences, Sun Yat-sen University, Guangzhou, China c School of Resource and Environmental Sciences, Wuhan University, Wuhan, China d Department of Chemistry, University of California, Irvine, CA, USA e Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China f College of Environmental Sciences and Engineering, Peking University, Beijing, China g Discipline of Chemistry, Faculty of Science and Technology, Queensland University of Technology, Australia h School of Chemistry and Biochemistry, University of Western Australia, Perth, Western Australia, Australia i Pacific Environment Limited, Perth, Western Australia, Australia j Department of Chemistry, National Central University, Taiwan HIGHLIGHTS GRAPHICAL ABSTRACT • Characteristics and sources of VOCs in China are reviewed. • Relationship of VOCs with O3 and SOA in China are reviewed. • Integrated literature review on the con- trol strategies of VOCs and photochem- ical smog is provided. • Future directions of VOC study in China are suggested. article info abstract Article history: Photochemical smog, characterized by high concentrations of ozone (O3)andfine particles (PM2.5) in the atmo- Received 2 July 2016 sphere, has become one of the top environmental concerns in China. Volatile organic compounds (VOCs), one of Received in revised form 13 September 2016 the key precursors of O3 and secondary organic aerosol (SOA) (an important component of PM2.5), have a critical Accepted 15 September 2016 influence on atmospheric chemistry and subsequently affect regional and global climate. Thus, VOCs have been Available online 14 October 2016 extensively studied in many cities and regions in China, especially in the North China Plain, the Yangtze River Keywords: Delta and the Pearl River Delta regions where photochemical smog pollution has become increasingly worse Volatile organic compounds over recent decades. This paper reviews the main studies conducted in China on the characteristics and sources Ozone of VOCs, their relationship with O3 and SOA, and their removal technology. This paper also provides an integrated Photochemical smog literature review on the formulation and implementation of effective control strategies of VOCs and photochem- China ical smog, as well as suggestions for future directions of VOCs study in China. © 2016 Elsevier B.V. All rights reserved. ⁎ Corresponding author. E-mail address: [email protected] (H. Guo). http://dx.doi.org/10.1016/j.scitotenv.2016.09.116 0048-9697/© 2016 Elsevier B.V. All rights reserved. 1022 H. Guo et al. / Science of the Total Environment 574 (2017) 1021–1043 1. Introduction “Synthesized Prevention Techniques for Air Pollution Complex and Inte- grated Demonstration in Key City Cluster Regions (3C-STAR) (2006– With rapid industrialization and urbanization in China, air pollution 2011)”, and the “Study of VOCs and Photochemical Ozone Pollution in associated with photochemical smog and haze-fog, characterized by the Pearl River Delta Region - Feasibility Study (2007–2010)” (Zhang high levels of ozone (O3)andfine particulates (PM2.5), has become et al., 2008b; Shao et al., 2009a; Louie et al., 2013). In addition, a number one of the most severe environmental pollution issues in many cities of research projects have been supported by the Ministry of Science and and regions of China (Zhang et al., 2008a, 2008b; Guo et al., 2009, Technology (MOST) State Center and the Ministry of Environmental 2013; Wang and Hao, 2012; Huang et al., 2014; Lee, 2015). The most Protection (MEP) to help understand the current status of air pollution polluted regions include the North China Plain (NCP; Beijing-Tianjin- in China (Hao et al., 2007; Wang et al., 2010a, 2010b; Wang and Hao, Hebei region), Yangtze River Delta (YRD; Shanghai-Jiangsu-Zhejiang re- 2012). Therefore, it is timely to conduct a critical review on VOCs studies gion) and Pearl River Delta (PRD; Guangdong-Hong Kong-Macau re- in Chinese cities and regions. The cities selected in this review are situ- gion) (Chan and Yao, 2008). Based on data collected at air monitoring ated in the most polluted and highly urbanized regions, i.e., the NCP, stations in 74 cities throughout China (the largest and/or most polluted YRD, and PRD. Although VOCs were also studied in some cities beyond cities), it was found that the annual average concentration of PM2.5 the above regions, the number of these studies is relatively small com- exceeded the national ambient air quality standard of 35 μg/m3 in 71 pared to those in the aforementioned three regions. In addition, al- cities, with the highest average value of 115 μg/m3 (Liu et al., 2013a). though hundreds of research papers on VOCs in the above regions are The severity of PM2.5 pollution has promoted the implementation of available in journals written in Chinese, this review mainly focuses on China’s “Air Pollution Prevention and Control Action Plan”, aimed at re- publications about tropospheric VOCs in the international peer- ducing the concentrations of PM2.5 by 25%, 20% and 15% in the Beijing- reviewed journals. Moreover, as the composition of VOCs in the atmo- Tianjin-Hebei region, the Yangtze River Delta and Pearl River Delta re- sphere is complex, this paper only focuses on two categories of VOCs, gions by 2017, respectively, compared to a 2012 baseline. High O3 con- i.e., non-methane hydrocarbons (NMHCs) and carbonyl compounds, centrations exceeding the national air quality standards have also been the main species contributing to the formation of photochemical O3 observed frequently in the aforementioned regions, with continuous in- and SOA. It should be noted that even though we have aimed to cover creasing trends and the highest recorded 1-h O3 mixing ratio of the major representative findings of VOCs in the above cities and re- 286 ppbv, compared to the 1-h standard of 200 μg/m3 or about gions, some studies may be not included in this review. 100 ppbv (Wang et al., 2006, 2009; Wang et al., 2014a; Zhang et al., The contents of this review include the abundance and speciation of 2014). High concentrations of O3 and PM2.5 have detrimental effects VOCs (Section 2), sources of VOCs (Section 3), the relationship of VOCs on air quality, human health, visibility, climate change and ecological with O3 and SOA (Section 4) and the development of the removal tech- systems. Therefore, priority should be given to mitigating O3 and nology for VOCs (Section 5). Control strategies for VOCs/photochemical PM2.5 pollution in the most polluted cities and regions in order to affect smog are reviewed in Section 6, together with their implications, while a return to blue skies. the future direction of VOCs studies is proposed in Section 7. As key precursors of O3 and secondary organic aerosols (SOA), (im- portant constituents of PM2.5), volatile organic compounds (VOCs) are composed of hundreds of species, which are directly emitted into the at- 2. Abundance and speciation of VOCs mosphere from a variety of natural and anthropogenic sources. The major anthropogenic emission sources of VOCs include vehicular ex- Since the properties of VOCs, such as toxicity, O3 and SOA formation haust, fuel evaporation, industrial processes, household products and potentials depend strongly upon the concentrations and chemical com- solvent usage (Guo et al., 2011). Controlling VOCs emissions can be positions of VOCs, the abundance and speciation of VOCs have been ex- helpful to alleviate photochemical smog in cities and regions in China, tensively studied. One of the first speciated VOCs sampling campaigns in especially because the production of O3 in urban areas is usually limited China was undertaken in 2001 (Barletta et al., 2005), in which VOCs by VOCs and because the loadings of SOA in PM2.5 have become more were collected in 43 Chinese cities in the cold season (January and Feb- significant in recent years (Huang et al., 2014; Cheng et al., 2010a, ruary). Since then, many efforts have been made to characterize the 2010b; Zhang et al., 2008a; Xu et al., 2008a, 2008b). Nevertheless, the VOCs in various regions of China, particularly in the regions of NCP, development of an effective strategy to reduce photochemical smog in YRD and PRD, as shown in Fig. 1. megacities based on the management of VOCs emissions is still prob- Table 1 summarizes the main techniques used to analyze the chem- lematic since each VOCs varies distinctly from others in its abundance ical compositions of VOCs in air samples. Generally, the methods to ob- and reactivity, which results in the nonlinear dependence of photo- tain VOCs concentrations can be divided into online measurement and chemical O3 and SOA formation on VOCs. Furthermore, due to the dual offline analysis. Whichever method is used, three units are integrated roles of nitrogen oxides (NOx)inO3 formation (fueling O3 formation in the analysis system, i.e., a pre-concentrator unit, a separation unit in low NOx environment and titrating O3 in high NOx environment), and a detection unit.