But that’s not the case: microplastics in clouds can affect the weather
From the depths of the seas to snow on mountains and even the air above cities, microplastics are increasingly appearing. Now at ACS Environmental science and technology lettersResearchers analyzed microplastics found in clouds over mountains. They suggest that these small particles could play a role in cloud formation, and thus influence the weather.
Microplastics – plastic fragments smaller than five millimeters – originate from countless everyday items, such as clothing, packaging and car tires. As research in this field develops, scientists are not only discovering microplastics in the atmosphere, but also investigating how they play a role in cloud formation. For example, a group of researchers recently discovered plastic beads, with surfaces that attract water, in clouds on Japanese mountaintops. So, to learn more, Yan Wang and his colleagues set out to look for microplastics in mountain clouds, used computer models to figure out how they might get there, and tested how the particles might affect—and be affected by—clouds.
Wang and his team first collected 28 liquid samples from clouds atop Mount Tai in eastern China. They then analyzed the samples and found:
- Low-altitude, denser clouds contain greater amounts of microplastics.
- The particles are made from common polymers, including polyethylene terephthalate, polypropylene, polyethylene, polystyrene, and polyamide.
- Microplastics tend to be smaller than 100 micrometers in length, although some are up to 1,500 micrometers long.
- Older, rougher particles have more lead, mercury and oxygen attached to their surfaces, which the researchers suggest may facilitate cloud evolution.
To investigate the source of the plastic particles in the clouds, Wang and the team developed computer models that approximate how the particles traveled to Mount Tai. These models indicate that airflow from densely populated inland areas, rather than from over the ocean or other nearby mountains, served as the primary source of the fragments. In laboratory experiments, researchers have demonstrated that microplastics exposed to cloud-like conditions — ultraviolet light and filtered water from cloud sources — have smaller sizes and rougher surfaces than those exposed to pure water or air. In addition, particles affected by cloud-like conditions had more lead, mercury, and oxygen-containing groups. These results suggest that clouds modify microplastics in ways that could enable molecules to influence cloud formation and the fate of airborne metals. The researchers concluded that more work is needed to fully understand how microplastics affect clouds and weather.
The authors acknowledge funding from the National Natural Science Foundation of China.