The Urban-Rural Transformation and Its Influencing Mechanisms on Air Pollution in the Yellow River Basin

Air pollution has recently gained much attention from the general population. Despite pollution control being an issue in both urban and rural regions, most of the available research has concentrated on urban districts. Hence, investigations into how urban-rural transition affects PM2.5 are warranted within the framework of urban-rural integration. Using the Yellow River Basin as a case study, this study employed the entropy method and Analytic Hierarchy Process (AHP) to uncover the extent of urban-rural transformation. It then used the spatial autocorrelation method to investigate the spatiotemporal features of PM2.5 and the spatial econometric model to investigate the mechanisms that influence the relationship between urban-rural transformation and PM2.5. The results are as follows: (1) The level of urban-rural transformation shows an obvious upward trend with time. The development has progressed from asymmetrical north-east and south-west elevations to a more balanced pattern of north-east, middle-east, and west-west elevations. (2) The PM2.5 concentration increased steadily, then fluctuated, and finally decreased. Notably, the general pattern has not changed much, and it is high in the east and low in the west. (3) Different subsystems of the urban-rural transformation have different impacts on air pollution at different stages. The influence of industrial transformation (IT) on PM2.5 showed an inverted "N-shaped" curve of negative-negative-changes, and the industrial structure played a leading role in the spatiotemporal evolution of PM2.5. An inverted "U-shaped" curve forms the left side of the impact of population transition (PT) on PM2.5. Land transformation (LT) has a "U-shaped" curve for its effect on PM2.5. This study provides a new perspective on the topic of PM2.5 and its connection to urban-rural integration, which is crucial to understanding the dynamics of this shift. To achieve the goal of high-quality development, this study supports regional initiatives to reduce PM2.5 emissions in the Yellow River Basin. Moreover, the results of this study can provide a reference for decision-makers in the world's densely populated areas that suffer from serious air pollution.