PM<sub>2.5</sub> Concentration Gap Reduction between\nTypical Urban and Nonurban China from 2000 to 2023

Since 2013, stringent clean air initiatives have significantly\nreduced atmospheric pollutant emissions in China, improving air quality\nand altering the spatiotemporal patterns of pollution. Utilizing fine\nparticulate matter (PM<sub>2.5</sub>) and its chemical composition\ndata from 2000 to 2023, we observed a reduction in the disparity of\nPM<sub>2.5</sub> concentrations between urban and nonurban areas.\nThis reduction is linked to stricter emission controls in urban areas\nand the relocation of some emission sources to nonurban areas. However,\nthe specific chemical constituents of PM<sub>2.5</sub> and the driving\nfactors behind these changes remain to be fully elucidated. By analyzing\nthe proportions of PM<sub>2.5</sub> components in major cities such\nas Beijing, Shanghai, and Guangzhou and their surrounding nonurban\nareas, we found that the narrowing gap in PM<sub>2.5</sub> concentrations\nbetween urban and nonurban regions is associated with the convergence\nof the organic matter (OM) proportions in both areas. This convergence\nresults from varying emission reduction strategies tailored to the\ndistinct characteristics of urban and nonurban pollution sources in\nChina. Coordinated governance between urban and nonurban areas should\nbe considered, along with the implementation of integrated control\nand mitigation measures for multiple pollutants to further enhance\nair quality in China.