Unveiling the seasonal transport and exposure risks of atmospheric microplastics in the southern area of the Yangtze River Delta, China

This study investigates the prevalence and impacts of suspended atmospheric microplastics (SAMPs) in the coastal metropolitan city of Ningbo in the Yangtze River Delta Region, China. The sampling was conducted at both urban centre and urban-rural fringe areas, near the coast but distant from large urban populations. SAMP abundance ranged from 0.017 to 0.430 items m^-³, with an average of 0.145 ± 0.09 items m⁻³. The urban centre exhibited approximately 70% more SAMPs than the urban-rural fringe, highlighting the influence of population density and human activity on microplastic pollution. Fibres dominated SAMP composition at both sites, while urban samples featured a greater variety of microplastic forms, such as fragments, beads, and films. Rayon and Polyethylene terephthalate were the predominant polymers, which were found to be directly related to local industrial activities. SAMPs ranged in size from 20 μm to 4984.4 μm, with over 60% smaller than 1000 μm. Seasonal variation followed a winter > autumn > spring > summer pattern. Correlation and principal component analyses identified atmospheric temperature, pressure, wind speed, and rainfall as key factors influencing SAMP abundance. Notably, backward trajectory analysis showed that oceanic air masses carried significantly fewer SAMPs compared to terrestrial air, diluting concentrations in coastal regions. Annually, an estimated 4.67 × 10¹³ microplastics are suspended over Ningbo. This is the first comprehensive study of SAMP pollution in this region, revealing interactions between local sources, environmental variations, air mass dynamics, and exposure. The findings underscore the need for targeted strategies to mitigate atmospheric microplastic pollution in coastal urban environments.