Influence mechanism of urban polycentric spatial structure on PM2.5 emissions in the Yangtze River Economic Belt, China

Urban spatial structure has important impact on environmental pollutant emissions, but few studies have investigated the possibility of a bidirectional influence mechanism between the two. This study used panel data of 108 prefecture-level cities in the Yangtze River Economic Belt (China) from 2009 to 2018. The objective was to test empirically the dynamic emission reduction effect of polycentric spatial structure on environmental pollution using the STIRPAT model as a framework to decipher the bidirectional causality effect. System generalized method of moments and the Sobel Test were applied to construct a panel intermediary effect model to verify the mechanism of urban polycentric development mode on urban haze pollution in China. Results showed that the urban polycentric structure in the Yangtze River Economic Belt has produced substantial pollution reduction effects, and that there are heterogenous regional, size, and functional differences in the impact of urban spatial structure of the Yangtze River Economic Belt on the environment. Moreover, the results of the intermediary effect test showed that market integration and industrial structure optimization are important ways via which to improve environmental pollutant emissions using the polycentric spatial development model. On this basis, suggestions were proposed for optimizing urban spatial structure to promote high-quality development of the Yangtze River Economic Belt.