[Orographic Influences on the Spatial Distribution of PM_2.5 on the Fen-Wei Plain]

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 PM_2.5. Topography is, therefore, an essential variable for understanding the spatial distribution of PM_2.5, especially in basin areas. Based on gridded data and both natural and human indexes, this paper examines orographic effects on the distribution of PM_2.5 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 PM_2.5 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, PM_2.5 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.