Microplastic–Cloud Interactions and the Potential Impacts On Cloud Formation

In a study published in ACS’ Environmental Science & Technology Letters, researchers have investigated the presence of microplastics in clouds above mountains.

This expands the scope of microplastic detection from the depths of the seas to mountain snow and even the air above cities. The findings suggest that these minuscule particles may have an impact on cloud formation, potentially influencing weather patterns.

Microplastics, defined as plastic fragments smaller than 5 mm, originate from various everyday items such as clothing, packaging, and car tires. As scientific research in this field progresses, not only are scientists detecting microplastics in the atmosphere, but they are also exploring the potential role these particles may play in cloud formation.

For instance, recent research identified plastic granules with water-attracting surfaces in Japanese mountaintop clouds. To research deeper into this phenomenon, Yan Wang and colleagues conducted a study to investigate the presence of microplastics in mountain clouds. They used computer models to understand how these particles might have reached the clouds and tested the potential impact of microplastics on and their interaction with cloud formations.

Wang and the research team initially gathered 28 liquid samples from clouds located at the summit of Mount Tai in eastern China. Subsequently, they conducted a detailed analysis of these samples and discovered the following:

• Particles are made of common polymers, including polyethylene terephthalate, polypropylene, polyethylene, polystyrene, and polyamide.
• The microplastics were smaller than 100 µm in length, and some are as long as 1500 µm.
• Low-altitude and denser clouds have greater amounts of microplastics.
• Older, rougher particles have more lead, mercury, and oxygen on their surfaces, which the researchers suggest could facilitate cloud development.

To investigate the origin of plastic particles in the clouds, Wang and the research team developed computer models to approximate the trajectory of these particles to Mount Tai. The models indicated that the primary source of the fragments was airflow from densely populated inland areas rather than from the ocean or nearby mountains.

In laboratory experiments, the researchers exposed microplastics to cloud-like conditions involving ultraviolet light and filtered water collected from clouds. The results showed that microplastics subjected to these cloud-like conditions exhibited smaller sizes and rougher surfaces compared to those exposed to pure water or air.

Furthermore, these particles had more lead, mercury, and oxygen-containing groups. These findings suggest that clouds can alter microplastics in ways that may impact cloud formation and the fate of airborne metals. The researchers emphasize the need for further research to fully comprehend how microplastics influence clouds and weather patterns.

The study was funded by the National Natural Science Foundation of China.

Journal Reference

Xu, X., et al. (2023). Characterization of Microplastics in Clouds over Eastern China. ACS Publication. doi.org/10.1021/acs.estlett.3c00729.