Since the environmental quality in metropolitan areas has significant impact on public health and everyday life of urban residents, it is of great importance to provide scientific information about the urban air pollutant concentration, which has gained much concern from both the governmental authorities and the scientific fields. This study illustrated the urban air quality of 113 sample cities in China by the comparison between the aggregate air quality index (AAQI) and the air quality index (AQI) and then depicted its spatial differentiation based on spatial interpolation. Furthermore, this study analyzed the influential factors behind the air quality variations among these cities by employing panel data models. The results indicated that the urban air quality showed a significant agglomeration feature at the national scale, with North China retaining the highest values both in terms of AAQI and AQI. From temporal perspective, the urban air quality reported a desirable trend nationwide from 2014 to 2016. Results from the regression models indicated that the urban air quality was affected by geographical locations, socioeconomic factors, and environmental regulations, among which urbanization level and industrial structure were reported to be the important socioeconomic factors exerting more significant impacts on the urban air quality. We suggest that more efforts should be devoted to develop comprehensive indices for evaluation of the urban air quality and to explore new avenues to improve urban air quality from industrialization and urbanization perspectives.
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