Metropolitan atmospheric microplastics: Characteristics and its inputs to fluvial system.

As a significant pathway for microplastics (MPs) contamination in aquatic environments, atmospheric deposition plays a critical role in the global MPs cycle. This study investigates atmospheric MPs pollution across urban, suburban, and exurban areas of Chengdu, China. The abundances decreasing from urban (246 n/(m²·day)) to suburban (192 n/(m²·day)) and exurban (177 n/(m²·day)) regions ("n" denotes the number of microplastic), dominated primarily by fibers and fragments. Principal Component Analysis (PCA) for MPs source appraisal identified three major underlying patterns, collectively explaining 73.9 % of the total variance. The dominant component (55.1 %) represents a mixed source of daily plastic products, which is pervasive across all regions. Correlation analyzes reveal that atmospheric MPs abundance in this megacity is positively correlated with precipitation intensity, shows a weak association with wind direction, and exhibits no significant correlation with temperature or humidity. Anthropogenic activities are found to exert a substantial influence on atmospheric MPs levels, while no clear relationship is observed between MPs and other air pollutants, suggesting distinct emission sources. Hydrological analysis tool quantified the total atmospheric MPs input to the local fluvial system during the annual rainy season, ranging from 689.07 to 1088.37 kg. The findings provide a quantitative foundation for assessing the role of atmospheric deposition in urban plastic pollution and support the development of targeted mitigation strategies in megacities.