Spatiotemporal variation of PM2.5 concentrations and its relationship to urbanization in the Yangtze river delta region, China

Having experienced a rapid urbanization and socioeconomic development, China is now facing a serious PM2.5 pollution issue. Based on the PM2.5 concentration data during 2000-2016 in the Yangtze River Delta region, the study analyzed the spatiotemporal variation of PM2.5 concentrations. The study also examined the correlation between PM2.5 concentrations and urbanization by using the correlation analysis as well as bivariate local indicators of spatial association analysis. Furthermore, we constructed the Environmental Kuznets Curve (EKC) model to investigate their evolution relationship. The results showed that PM2.5 concentrations generally increased during 2000-2016. In most cities of the northeast of this region, PM2.5 concentrations were high; but the increased trend were relatively slow. There was a positive correlation between urbanization and PM2.5 concentrations. However, there was a negative correlation between urbanization and the variation trend of PM2.5 concentrations. There was a relationship of "high-high" aggregation between urbanization and PM2.5 concentrations in cities of southern Jiangsu province; and a relationship of "low-low" aggregation in cities of southern Zhejiang province. PM2.5 concentrations had a pattern of inversed-U shape with urbanization. These findings and the policy suggestions can contribute to effective policymaking aimed at abating PM2.5 pollution from the perspective of urbanization development.