Topography not only has an effect on the spatial distribution of pollutants by restricting populations and industrial activities, but also affects the formation, transmission, accumulation, diffusion, and sedimentation of PM2.5. Topography is, therefore, an essential variable for understanding the spatial distribution of PM2.5, especially in basin areas. Based on gridded data and both natural and human indexes, this paper examines orographic effects on the distribution of PM2.5 on the Fen-Wei Plain based on the change point method, regression, the geographical detector method, and bivariate spatial autocorrelation. The results indicate that:① The relief amplitude of the plain is generally lower in its central part than at its edge, which is similar to the attitudinal distribution in this region; ② The distribution of PM2.5 is negatively related to relief amplitude, with high concentrations in central area and lower concentrations at the edge; ③ Based on the geographical detector analysis, PM2.5 patterns in this region are shaped by human factors including population, gross domestic product(GDP), and energy consumption, as well as natural factors including meteorological conditions and vegetation; and ④ Topography has a significant effect on both human and natural factors; an increase of relief amplitude is associated with a decrease in population, GDP, and energy consumption based on power function. Accordingly, temperature goes down linearly; precipitation, relative moisture, and wind speed increase linearly; and the vegetation index increases based on a logarithmic function.
Keywords: Fen-Wei Plain; concentration of PM2.5; orographic influence; relief amplitude; spatial distribution.