Abstract
Air pollution has impacted people’s lives in urban China, and the analysis of the distribution and driving factors behind air quality has become a current research focus. In this study, the temporal heterogeneity of air quality (AQ) and the dominant air pollutants across the four seasons were analyzed based on the Kruskal-Wallis rank-sum test method. Then, the spatial heterogeneity of AQ and the dominant air pollutants across four sites were analyzed based on the Wilcoxon signed-rank test method. Finally, the copula model was introduced to analyze the effect of relative factors on dominant air pollutants. The results show that AQ and dominant air pollutants present significant spatiotemporal heterogeneity in the study area. AQ is worst in winter and best in summer. PM10, O3, and PM2.5 are the dominant air pollutants in spring, summer, and winter, respectively. The average concentration of dominant air pollutants presents significant and diverse daily peaks and troughs across the four sites. The main driving factors are pollutants such as SO2, NO2, and CO, so pollutant emission reduction is the key to improving air quality. Corresponding pollution control measures should account for this heterogeneity in terms of AQ and the dominant air pollutants among different urban zones.
Highlights
Urban air pollution has become an issue of global concern [1,2,3,4], in rapidly developing countries like China [5,6,7,8]
The Kruskal-Wallis rank-sum test method is suitable for testing the differences at a significant level of 5% between the seasonal AQI, because there is no paired relationship in the seasonal AQI data at each site and the distribution type and parameters for AQI is unknown
The spatiotemporal heterogeneity of pollution distribution can be systematically analyzed by using a method based on the Kruskal-Wallis rank-sum test and the Wilcoxon signed-rank test
Summary
Urban air pollution has become an issue of global concern [1,2,3,4], in rapidly developing countries like China [5,6,7,8]. According to a World Bank study, 16 of the top 20 most polluting cities in the world are located in China [9,10,11], concentrated in Northern China and Eastern China [8,12,13,14,15,16]. The concentration of dominant pollutants is higher in northern Chinese cities than in those of Western and South-eastern China, and the number of days with high pollution is greatest in winter and spring and lowest in summer and autumn [12,16,32,33]. The main reasons for the nationwide spatiotemporal heterogeneity in Northern China are that there is more carbon emission in winter [16,32,33]
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