Abstract
Fine particles are a crucial air pollutant in terms of their impact on the ambient environment, citizens’ health and traffic visibility. In this study, temporal and spatial variations in PM2.5 were analyzed in Beijing, Shanghai, Guangzhou, Chengdu and Shenyang in China from June 2013 till May 2017 using hourly data collected from the U.S. Embassy and Consulate monitoring system. The distributions of the annual, seasonal, monthly and diurnal concentration were illustrated by the attainment rate and the severity rate, as well as the length of time. After that, the coefficient of divergence (COD) was adopted to study the spatial heterogeneity among five typical megacities. Additionally, the relationship between PM2.5 and meteorology was calculated by Pearson’s correlation and stepwise multiple linear regression. The results show that annual PM2.5 concentrations were overall downward trends in all areas. Clear seasonal variations were identified, with the least pollution in summer and the most in winter. The hourly distribution was dramatically different, while the average concentration during the daytime was higher than at night except in Shanghai, and the weekends had higher pollution than the weekdays except in Chengdu. Also, the monthly attainment rate displayed an inverted-U distribution; oppositely, the severity rate revealed a U-shaped distribution. With the increasing pollution levels, the duration of the PM2.5 pollution was observed to be continuously declining in Guangzhou, Shanghai and Beijing but fluctuating in the other two cities. Furthermore, COD values indicated that there was an obvious spatial heterogeneity between Beijing–Chengdu–Shenyang and Shanghai–Guangzhou. As for meteorology, the pressure had a significantly positive impact on the PM2.5 concentration, while the temperature and rainfall had a negative influence. These results show the pollution levels of PM2.5 in different cities at distinct times and confirm the important role of meteorological conditions in air quality. The findings also provide forecast models of PM2.5 for the five cities.
Highlights
The experience of many countries demonstrates that economic development will inevitably bring about a certain degree of environmental problems; China is no exception (Guo et al, 2017b; Wang et al, 2017c)
The results show that annual PM2.5 concentrations were overall downward trends in all areas
The PM2.5 hourly data was selected from the period between June 2013 and May 2017 from the U.S Embassy and Consulate monitoring system; at the same time, monthly meteorological data from the China Meteorological Yearbook for June 2013–December 2014 was used
Summary
The experience of many countries demonstrates that economic development will inevitably bring about a certain degree of environmental problems; China is no exception (Guo et al, 2017b; Wang et al, 2017c). The former is targeted at one or several cities (Lowsen and Conway, 2016; Gulia et al, 2017), such as megacities Beijing and Shanghai (Yan et al, 2016; Fontes et al, 2017) The latter is a hot area that is composed of multiple monitoring sites (Wang and Fang, 2016; Bran and Srivastava, 2017; Zikova et al, 2017), such as the Yangtze River Delta in China (Hu et al, 2014; Xu and Jiang, 2015), as well as the whole country as an object
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