Characterization of Microplastics in Clouds over Eastern China

Airborne microplastics (MPs) have the potential to travel a long distance and undergo several cloud processes through atmospheric transport. However, little is known about the interactions between MPs and clouds. Here, we present field evidence for the presence of abundant and various MPs in cloudwater samples collected at Mt. Tai (1545 m asl.) in eastern China, with an average concentration of 463 MP L-1 in cloudwater, i.e., 0.21 MP m(-3) in air. The cloud MPs had a broad size range of 8-1542 mu m with 60% being smaller than 100 mu m and dominant shapes of fragments with diverse polymers and darker colors. The concentrations of MPs were influenced by cloud liquid water content, source regions, and trajectory height, while the shapes and sizes appeared to be associated with long-range transport or localized sources. The roughened surface of cloud MPs indicated photochemical aging, which likely increased their adsorption capability for toxic metals (e.g., Pb, Hg) as confirmed by laboratory photoaging and adsorption simulations in ambient air, ultrapure water, and cloudwater. More research is needed to understand microplastic-cloud interactions and the potential impacts on atmospheric metal cycles and cloud formation.