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 μm with 60% being
smaller than 100 μm 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.