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Review
. 2020 Oct;12(10):6396-6410.
doi: 10.21037/jtd-19-crh-aq-004.

Trends in ambient air pollution levels and PM2.5 chemical compositions in four Chinese cities from 1995 to 2017

Zixuan Yin  1 , Xiaofeng Huang  1 , Lingyan He  1 , Suzhen Cao  2 , Junfeng Jim Zhang  3   4   5
Affiliations
Free PMC article
Review

Trends in ambient air pollution levels and PM2.5 chemical compositions in four Chinese cities from 1995 to 2017

Zixuan Yin et al. J Thorac Dis. 2020 Oct.
Free PMC article

Abstract

An in-depth analysis of the specific evolution of air pollution in a given city can provide a better understanding of the chronic effects of air pollution on human health. In this study, we reported trends in ambient concentrations of particulate matter (PM) and gaseous pollutants [sulfur dioxide (SO2), nitrogen dioxide (NO2), and ozone (O3)] from 1995 to 2017 and PM2.5 composition for the period of 2000-2017 in Guangzhou, Wuhan, Chongqing, and Lanzhou. We provided socio-economic indicators to help explain the pollution trends. SO2 and PM (including PM10 and PM2.5) concentrations showed a downward trend in recent years with the most notable reduction in SO2 in Chongqing and PM2.5 in Guangzhou. There was an overall flat trend for NO2, while O3 showed an upward trend in recent years except in Lanzhou. The majority of PM2.5 mass was SO4 2- (6.0-30 µg/m3) and organic carbon (6.0-38 µg/m3), followed by NO3 - (2.0-12 µg/m3), elemental carbon (2.1-12 µg/m3), NH4 + (1.0-10 µg/m3), K+ (0.2-2.0 µg/m3), and Cl- (0.2-1.9 µg/m3). Except for secondary inorganic aerosols in Wuhan, annual average concentrations of all PM2.5 constituents showed a declining trend after 2013, corresponding to the trend of PM2.5. The secondary sources in PM2.5 were found to be most prominent in Wuhan, while the most abundant EC and Cl- in Lanzhou was attributed to the use of coal. Despite temporal and spatial variabilities across the four cities, coal combustion, traffic emissions, and secondary pollution have been the major sources of PM2.5 pollution. These trends in ambient air pollution levels and PM2.5 composition may help understand changes in health outcomes measured at different times within the time period of 1995-2017 in the four cities.

Keywords: Air pollution; PM2.5; chemical composition; long-term variation; source.

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Conflict of interest statement

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at doi: http://dx.doi.org/10.21037/jtd-19-crh-aq-004). The issue “Children’s Respiratory Health and Air Quality” was commissioned by the editorial office without any funding or sponsorship. JJZ served as the unpaid Guest Editor of the issue. JJZ also serves as an unpaid editorial board member of Journal of Thoracic Disease. The other author has no other conflicts of interest to declare.

Figures

Figure 1
Figure 1
Map showing the four cities included in this study, including Lanzhou (LZ), Wuhan (WH), Chongqing (CQ), and Guangzhou (GZ).
Figure 2
Figure 2
Temporal variations in five major air pollutants in four cities: (A) SO2, (B) NO2, (D) PM10 for 1995–2017, (C) O3, (E) PM2.5, (F) PM2.5/PM10 for 2012–2017. The black dotted line indicates the second-level concentration standards of pollutants according to the government GB3095-2012 (43) standard. SO2, sulfur; O3, ozone; PM, particulate matter.
Figure 3
Figure 3
Spatiotemporal variation of mass fractions in major chemical composition of PM2.5 in the four cities prior to and after 2013. Digital label for every sector indicates the corresponding component proportion, and the size of each fan corresponds to the absolute concentration of PM2.5. PM, particulate matter.
Figure 4
Figure 4
Variations in the absolute concentrations (μg/m3) of examined PM2.5 and seven components before and after 2013 in LZ, WH, CQ, and GZ. Solid column represents the first period [2010–2013] while the dotted line column indicates the second period [2014–2017] in each component across four cities. PM, particulate matter; LZ, Lanzhou; WH, Wuhan; CQ, Chongqing; GZ, Guangzhou.
Figure 5
Figure 5
Comparisons of concentrations of five major metal elements during two periods [1996 and 2010–2017]. Solid column represents the first period [1996] while the dotted line column indicates the second period [2010–2017] for each component across four cities.
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