The imprint of urbanization on PM2.5 concentrations in China: The urban-rural gradient study

Abstract

• Urbanization imprint on PM 2.5 varied with scale and region. • N-shaped PM 2.5 pattern was found in relatively mature regions, urban agglomerations. • The positive linear pattern existed in the northwest, emerging urban agglomerations. • The diverse patterns of IQR highlighted the need of nuanced control strategies. Urbanization has been acknowledged as an important driver of PM 2.5 pollution, but the spatial heterogeneity within cities remain largely unexplored in understanding urbanization impacts on PM 2.5 . Here, we applied the urban-rural gradient approach to perform a comprehensive analysis of urbanization effects on PM 2.5 concentrations in China at the national, regional and urban agglomeration scales. Our results clearly revealed a heterogeneous imprint of urbanization on PM 2.5 across regions and within the same urbanization intensity (UI) under the context of economic development level and urbanization stage. We found an N-shaped PM 2.5 pattern along the urbanization gradient across the country, in the southeast of the Hu Huanyong line and relatively mature urban agglomerations namely BTH and YRD, whilst a positive linear pattern in the northwest of the Hu line and emerging urban agglomerations. Furthermore, diverse patterns of interquartile range (IQR) of PM 2.5 within the same UI suggested that tailor-made PM 2.5 pollution control strategies are dependent on specific urban contexts within and across cities. A generally low and stable mean and IQR of PM 2.5 concentration with increasing UI in the PRD, the first mover of urbanization and most mature urban agglomeration in China, indicated that nuanced regulatory solutions should target at maintaining its coordinated urban and rural development. A broadening IQR of PM 2.5 with increasing UI in the northwest of the Hu line and emerging urban agglomerations signified the promising potential to mitigate from scratch as urbanization is yet to be intensified there.