Characteristics of Spatiotemporal Differentiation and Spillover Effects of Land Use Coupled with PM2.5 Concentration from the Perspective of Ecological Synergy—A Case Study of the Huaihe River Ecological Economic Belt

Under the rapid urbanization process, PM2.5 pollution has become an increasingly critical issue. Changes in land-use types will inevitably affect PM2.5 concentration. Meanwhile, the problem of imbalance and inadequacy of regional development remains prominent. This study took the Huaihe River Ecological Economic Belt as the research object, integrating the spatial econometric model with the Geographically and Temporally Weighted Regression (GTWR) and Multiscale Geographically Weighted Regression (MGWR) models, to investigate the spatiotemporal heterogeneity and spillover effect of the association between PM2.5 concentration and land use from 1998 to 2021. The main findings are as follows: (1) PM2.5 concentration in the study area from 1998 to 2021 showed an upward and then a downward trend, taking 2013 as a turning point, with respective magnitudes of 50.4% and 42.1%; (2) land use exerts a significant spillover effect on PM2.5 pollution. Except for grassland and cropland, the direct effect of each land type on PM2.5 pollution exceeds its indirect effect; (3) the influence of land use on PM2.5 pollution exhibits significant spatiotemporal variations. The impact coefficient of forests remains relatively consistent across the entire region, whereas that of cropland, water bodies, and impervious surfaces varies markedly across different regions, particularly in the northeastern and southern cities of the study area. The results of this study may give new ideas for collective governance and joint environmental remediation in different cities and probably provide some basis for the formulation of air pollution control policies and urban land planning.