Published in the journal 'Environmental Science and Technology: Air', the study reveals that microplastics act as ice-nucleating particles - microscopic aerosols that encourage ice crystal formation within clouds.
This phenomenon could alter precipitation patterns, affect climate models, and even impact aviation safety, according to Miriam Freedman, a Penn State chemistry professor and senior author of the study. "Throughout the past two decades of research into microplastics, scientists have been finding that they're everywhere, so this is another piece of that puzzle," Freedman noted. "It's now clear that we need to have a better understanding of how they're interacting with our climate system, because we've been able to show that the process of cloud formation can be triggered by microplastics."
In laboratory settings, researchers analyzed how four types of microplastics - LDPE, PP, PVC, and PET - affect ice formation. The team suspended each plastic type in water droplets, cooling them gradually to observe ice nucleation. The findings indicated that these microplastics could cause water droplets to freeze 5-10 degrees Celsius warmer than usual. Under normal conditions, droplets without impurities freeze around -38 degrees Celsius. Lead author Heidi Busse, a Penn State graduate student, explained, "In the case of our microplastics, 50% of the droplets were frozen by minus 22 degrees Celsius for most of the plastics studied." The presence of microplastics introduced defects into the droplets, enabling ice nucleation at warmer temperatures.
While the full impact of these findings on weather and climate is not yet certain, Freedman highlighted that microplastics likely contribute to changes in cloud formation. Mixed-phase clouds, which contain both liquid and ice, play a key role in climate effects. When such clouds form in polluted areas with high aerosol concentrations, including microplastics, the available water is spread across more droplets, resulting in smaller droplet sizes and delayed rainfall. This process may lead to heavier rainfall once droplets coalesce and reach a sufficient size to precipitate.
Freedman explained that clouds generally cool the Earth by reflecting solar energy, but under certain conditions, they can also trap heat. The ratio of ice to liquid in a cloud influences its warming or cooling effect. If microplastics are changing this balance in mixed-phase clouds, their presence might be influencing climate patterns, though modeling this effect remains complex. "We know that the fact that microplastics can nucleate ice has far-reaching effects, we're just not quite sure yet what those are," Busse said. This interaction may influence climate at various levels, potentially intensifying storms or altering light scattering.
The team also examined how environmental aging - natural chemical changes due to exposure to light, ozone, and acids - affects microplastics' ice-forming ability. Aging reduced the ice-nucleation ability of LDPE, PP, and PET but increased that of PVC due to surface changes.
Future research will focus on additives commonly found in plastics to further understand how these particles influence atmospheric processes. "We know the full lifecycle of these plastic items we use every day could be changing the physical and optical properties of the Earth's clouds and, therefore, changing the climate in some way, but we still have a lot to learn about exactly what they are doing," Busse added.
Other contributors to this research include Penn State graduate students Devaka Ariyasena and Jessica Orris. The study was funded by the U.S. National Science Foundation and supported by the Penn State Materials Characterization Lab.
Research Report:Pristine and Aged Microplastics Can Nucleate Ice Through Immersion Freezing
Related Links
Penn State
Earth Observation News - Suppiliers, Technology and Application
| Subscribe Free To Our Daily Newsletters |
| Subscribe Free To Our Daily Newsletters |
