Abstract
ABSTRACT To evaluate the effectiveness of control strategies during the G20 Summit (August 24–September 6, 2016), five sites were selected for investigating the variation in air pollution in the city of Hangzhou and its surrounding areas. The results showed that the air quality in Hangzhou greatly improved after the implementation of strict emission controls. Compared to the same dates from the five preceding years, the G20 period exhibited low relative humidity during the early stage (August 27–31) and no significant differences in other meteorological conditions. The SO2, NO2, PM10, and PM2.5 concentrations averaged across the five sites in Hangzhou decreased by 42.6%, 57.1%, 36%, and 38.5%, respectively, although the average O3 concentration increased by 19%. These changes indicate that the emission reduction measures decreased the concentrations of several pollutants. Compared to the same dates from the previous year (August 24–September 6, 2015), the G20 period exhibited significantly decreased concentrations for most of the chemical components of PM2.5, particularly SO42–, NO3–, and NH4+. Additionally, the aerosol optical depth (AOD) and the NO2 column densities were found to exhibit similar trends with that of the pollutants in this city.
Highlights
Characterized by fine particles (PM2.5), nitrogen oxides (NOx), and ozone (O3), regional air pollution has been increasingly prominent in China in recent years due to the rapid development of urbanization and industrialization (Chan and Yao, 2008)
The possible reason for the increase in O3 concentration during the G20 period in 2016 is that the NOx emission control measures were stronger than the VOCs emission control measures, which resulted in the weak inhibition of NOx on O3 production and significant increase of O3 concentrations (Xing et al, 2011; Yarwood et al, 2013)
Biogenic VOC (BVOC) emissions play an essential role in O3 formation because they are highly reactive hydrocarbons that cause the rapid increase of O3 when oxidized by hydroxyl radicals (Geng et al, 2011; Situ et al, 2014)
Summary
Characterized by fine particles (PM2.5), nitrogen oxides (NOx), and ozone (O3), regional air pollution has been increasingly prominent in China in recent years due to the rapid development of urbanization and industrialization (Chan and Yao, 2008). Strict short-term emission controls have effectively improved the air quality during several special events such as the Beijing Olympics in 2008, the Asia-Pacific Economic Cooperation (APEC) meeting in November 2014, the Nanjing Youth Olympic Games in 2014, and the China Victory Day Parade in 2015. These short-term emission controls provide an ideal opportunity for evaluating our current understanding of the formation mechanisms of air pollution and exploring the impact of alternative control options to aid in the formulation of more effective policies for emission reduction
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