Microplastics are more than just an annoying pest plaguing the Earth. They also seem to influence the weather and climate.
No doubt you have read it somewhere: microplastics are everywhere, on the top of Mount Everest and in the depths of the Mariana Trench, in the stomachs of sea turtles, in the roots of plants and in our own lungs. And of course they also go through the air. This is not without consequences, as researchers at Penn State University now have presented. The microplastics encourage the formation of ice crystals in clouds. In this way, they can influence precipitation patterns, weather forecasting and climate models.
A piece of the plastic puzzle
Miriam Freedman, professor of chemistry at Penn State, said: “Over the past two decades, scientists have discovered that microplastics are everywhere, and this is one more piece of the puzzle that. It is now clear that we need to know more about the interaction of plastics with our climate system, as we have shown that cloud formation can be fueled by microplastics.”
In a controlled laboratory environment, the researchers studied what happened when four different types of microplastics – low density polyethylene (LDPE), polypropylene (PP), polyvinyl chloride (PVC) and polyethylene terephthalate (PET) – to suspend in small drops of water. and let it cool slowly. They could therefore see how the microplastics affected the formation of ice.
Faster freezing
What it turned out was that the average temperature at which the droplets froze was 5 to 10 degrees higher than droplets without microplastics. Normally, a water droplet freezes in the atmosphere at about -38 degrees Celsius. Any type of impurities in the water droplet, be it dust, bacteria or microplastics, can provide a structure around which ice crystals form, causing the water to freeze even at higher temperature.
“In our tests, 50 percent of the droplets were frozen at -22 degrees for most of the plastics tested,” says researcher Heidi Busse. “If you add something insoluble, you introduce a defect in the droplet, which allows ice formation to occur at a higher temperature.”
It is not yet entirely clear what this discovery means for our climate and weather, but it seems that microplastics are already having an impact. For example, common clouds, such as cumulus, stratus, and nimbus clouds, contain a mixture of liquid and frozen water and are widespread in the atmosphere. Microplastics can already have a big impact on this.
heavier showers
“If air pressure patterns cause droplets to lift and cool, microplastics could affect weather patterns and form ice in the clouds,” Freedman said. “In a polluted environment with many more aerosols such as microplastics, the available water is distributed among many more aerosol particles, creating smaller droplets around each particle. When you have more droplets, there will be less rain, but because droplets only make rain once they are big enough, the cloud collects more water before the droplets fall, leading to heavier rain.”
In general, clouds cool the Earth by reflecting the sun’s rays, but certain clouds at certain altitudes can trap heat and have a warming effect. The ratio of liquid water to ice in clouds is definite. If microplastics affect cloud formation, they may also affect the climate, although it is still very difficult to map their full impact.
Stronger the storm
“The fact that microplastics can accelerate the formation of ice has far-reaching implications, but we still don’t know exactly what the impact is,” says Busse. “We can look at this at different levels. For example, ‘ it could lead to more powerful storms, but also cause changes in the distribution of light, which could have a much greater impact on our climate.”
A small bright spot: the age of the microplastics appeared to have a beneficial effect. The researchers simulated the aging process by exposing the plastic particles to light, ozone and acids to see if this changed their ability to form ice. All plastics were still able to form ice, but this became less effective with age. Only in PVC did age develop the ability to form ice, possibly due to minor surface changes.
Still a lot to learn
Although many are still uncertain about the precise effects. “We know that the entire life cycle of the plastic materials we use every day can change the physical and optical properties of clouds, thus affecting the climate in some way, but we still have a lot to learn about exactly what they do,” concluded Bus.
2024-11-10 12:02:00
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