Summit of Mount Tai in Eastern China. Credit: Dirrival
Key points:
- Researchers analyzed microplastics in clouds at the top of Mount Tai in eastern China.
- They found that low-altitude and denser clouds contained greater amounts of microplastics than others.
- They also discovered that older, rougher particles had more lead, mercury and oxygen, which the could facilitate cloud development and impact weather.
From sea to shining sea, scientists have consistently found and reported on the many microplastics polluting Earth’s oceans. Now, researchers have looked skyward—and found the same pollution.
In a new study published in ACS’ Environmental Science and Technology Letters, researchers analyzed microplastics in clouds above mountains. Their findings suggest that these tiny particles could play a role in cloud formation and, in turn, affect weather.
For the study, researchers collected 28 samples of liquid from clouds at the top of Mount Tai in eastern China. The results showed that low-altitude and denser clouds contained greater amounts of microplastics than others. The microplastics were made of common polymers, including polyethylene terephthalate, polypropylene, polyethylene, polystyrene and polyamide. They tended to be smaller than 100 micrometers in length, although some were as long as 1,500 micrometers. The researchers found that older, rougher particles had more lead, mercury and oxygen attached to their surfaces, which the researchers suggest could facilitate cloud development.
To investigate where the plastic particles in the clouds originated, the team developed computer models that approximated how the particles traveled to Mount Tai. These models suggested that airflow from highly populated inland areas, rather than from over the ocean or other nearby mountains, served as the major source of the fragments.
In laboratory experiments, the researchers demonstrated that microplastics exposed to cloud-like conditions—ultraviolet light and filtered cloud-sourced water—had smaller sizes and rougher surfaces than those exposed to pure water or air. Additionally, particles impacted by the cloud-like conditions had more lead, mercury and oxygen-containing groups.
These results suggest that clouds modify microplastics in ways that could enable the particles to affect cloud formation and the fate of airborne metals. The researchers conclude that more work is needed to fully understand how microplastics affect clouds and the weather.