Air pollution transmission networks in China's urban agglomerations: Drivers and vulnerabilities

The cross-regional transmission of air pollution is a complex and urgent environmental challenge. Integrating complex network analysis with Quadratic Assignment Procedure (QAP) analysis and cascade failure theory, we examine the structure, drivers, and vulnerabilities of air pollution transmission networks across 11 Chinese urban agglomerations. We find that each agglomeration demonstrates high regional concentration and functional specialization, with distinct city roles. The Pearl River Delta exhibits strong bidirectional pollution transmission, while the Lanxi and Harbin-Changchun agglomerations show lower network density and reciprocity, mainly featuring unidirectional flows. Developed eastern regions consistently occupy core positions, while central China's network displays a decentralizing trend, shifting the pollution transmission center towards the central and western regions. Key drivers identified via QAP include economic development, vegetation coverage, and environmental regulation. Cascade failure analysis highlights that nodes with high betweenness centrality and high-weight edges are crucial vulnerabilities; targeted interventions at these strategic points can effectively reduce pollutant spread. This study offers integrated theoretical insights into the “structure-driver-vulnerability” mechanism of pollution transmission and provides practical guidance for sustainable regional governance, identifying critical nodes and developing targeted air quality management strategies.