Seasonal patterns and environmental drivers of atmospheric microplastics in a coastal megacity

Atmospheric microplastics (MPs) pose emerging environmental and health risks, yet their temporal dynamics, sources and environmental interactions in coastal cities remain poorly understood. To address this gap, a year-long atmospheric MPs monitoring campaign was conducted in Shanghai, employing microscopic and spectroscopic identification of particles, along with multi-indicator correlation analysis involving air pollutants, particulate components, and meteorological factors. Results showed an annual average MPs concentration of 0.08 P/m³, with significantly higher concentrations in winter than in other seasons (p < 0.05) and in the dry season (October-March) compared to the wet season (April-September). PET (42.86 %) was the dominant polymer, and fibers accounted for the highest proportion (∼82 %), showing distinct seasonal variations. MPs concentrations correlated positively with SO₂ (r = 0.55), indicating contributions from industrial emissions, and negatively with O₃ (r = -0.41), suggesting oxidative degradation. Positive correlations with Cl^- (r = 0.82) and Na⁺ (r = -0.53) implied marine aerosol influence, while the associations of PET, PE, and PP with Pb and K suggested potential sources from industrial emissions and biomass burning. Meteorological factors and marine monsoons climate significantly regulated MPs accumulation and removal, with low wind speeds in winter facilitating pollution accumulation, whereas wet-season southeasterly monsoons and precipitation enhanced particle removal and marine aerosol interactions. In conclusion, this study elucidates the spatiotemporal dynamics, sources, and local-regional mechanisms of atmospheric MPs in coastal cities, emphasizing the regulatory roles of meteorological and monsoonal factors. These findings provide scientific support for pollution control and policy development.