Riccardo Liguori Research led by Pennsylvania State University has found that the interaction of these tiny particles with atmospheric water could change precipitation patterns and weather patterns, raising concerns about the global climate future.
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Microplastics are plastic fragments less than 0.2 inches in size that have invaded even the most far-out and virginal nooks of Earth. From the bottom of the Mariana Trench to the snow-covered tips of Everest, they are everywhere.
Now, a new study by a team of researchers from Pennsylvania State University, published in ACSPublications, discloses an unexpected turn of events: microplastics can influence cloud formation, thereby affecting the global climate.
According to the study published in Environmental Science and Technology: Air, the microplastics act as ice-nucleating particles, or microscopic seeds that enable the formation of ice crystals in clouds. It’s a well-known process among atmospheric scientists, who say it’s fundamental for determining behavior in clouds, which in turn determines weather events such as rainfall and temperature.
How microplastics change clouds
To study the impact of microplastics, researchers in Penn State studied four common kinds of plastic that exist in the environment, such as LDPE, polypropylene (PP), polyvinyl chloride (PVC), and polyethylene terephthalate (PET). The microplastics were suspended in tiny droplets of water, cooled to observe how their presence impacted ice formation.
Surprisingly, the mean freezing temperature of droplets was between 41-50°F higher compared to droplets without microplastics. The usual freezing temperature for water droplets in normal atmospheric conditions is around -36.4°F (-38°C).
However, impurities like dust, bacteria, or microplastics might lower this threshold and enable the nucleation of ice at higher temperatures. “With microplastics, 50% of droplets froze at -7.6 °F (-22 °C),” according to Heidi Busse, a Ph.D. student and lead author of the study.
Implications for climate and rainfall
The result has direct implications for weather and climate modeling. Miriam Freedman, professor of chemistry at Penn State and senior author on the study, says microplastics in the atmosphere may already be affecting how clouds form and behave. “When air rises and cools, microplastics can serve as centers for ice formation,” says Freedman.
This will possibly alter the pattern and frequency of precipitation. In fact, under a more polluted environment, microplastic particles distribute water among more nuclei, forming smaller droplets that delay rainfall. In other words, with it, clouds can gather more water before releasing it, likely to enhance more violent and sudden events.
Clouds themselves are major active players in Earth’s thermal balance. They can cool or warm by reflecting part of the solar radiation or by trapping some of the heat emitted from the Earth’s surface, depending on altitude and composition. Similarly, there is the crucial effect of the quantity of liquid water and ice in a cloud on the reflectivity versus retention of heat. If microplastics are changing this balance, then they may be contributing to climate change already, although any proper quantification of the magnitude of such an effect is well beyond reach.
The influence of environmental aging
The scientists further investigated how the natural aging of microplastics-that is, photo-chemical processes due to light exposure, ozone and acids-may alter their ice-nucleation potency. In most cases, aging reduced the nucleation effectiveness of LDPE, PP, and PET while slightly increasing that of PVC due to slight changes in its surface.
These observations suggest that microplastics do respond to environmental and chemical parameters, yet another uncertainty factor added to the already complex models of climate. In the words of Busse, “The life cycle of the plastics we use daily could alter the physical and optical properties of clouds, influencing the climate in ways we are only beginning to understand.”
Next steps
The implications of this discovery will have to be further studied. Researchers will study the impact that chemical additives in plastics have, to determine if they further modulate the interaction with clouds.
As governments and international organizations consider actions to reduce plastic in the environment, science continues to uncover how much these tiny particles are remaking the world around us-even up in the skies.
