Multidimensional effects of urbanization on PM concentration in China.

Recently, the contradiction between urbanization and the air environment has gradually attracted attention. However, most existing studies have explored the impact of single urbanization factors, such as population, the economy, or land, on PM and ignored the impact of multidimensional urbanization on PM concentration. Moreover, the heterogeneity in the mechanisms responsible for the PM concentration caused by multidimensional urbanization has not been thoroughly studied in different regions in China. Therefore, we investigate the spatial-temporal evolution characteristics of PM concentration in China during 1998-2019 by spatial analysis and dynamic panel models based on the environmental Kuznets curve (EKC). Then, we study the effects of multidimensional urbanization on PM concentration, and analyze the dominant factors in China's eight economic regions. During the study period, the PM concentration in China fluctuated before 2013 and gradually decreased thereafter. The PM concentration has significant regional differences in China. Spatially, the PM concentration is higher in the north than in the south and higher in the east than in the west. Additionally, there is a significant spatial spillover effect. Both population urbanization and economic urbanization show an inverted U-shaped relationship with PM concentration in China, which is consistent with the classical EKC theory. Due to other socioeconomic factors, the PM concentration tends to decrease linearly with increasing land urbanization rate. The effects of urbanization on the PM concentration in the eight economic regions in China show significant differences. The effect of land urbanization on the PM concentration is dominant in the Middle Yangtze River region, that of economic urbanization is dominant in northwestern China, and that of population urbanization is dominant in the remaining regions in China.