Researchers investigate occurrence of microplastics in cloud water

Washington: Plastic particles less than 5 mm in diameter are referred to as ‘microplastics.’ These microscopic plastic particles are typically found in industrial effluents or as a result of the decomposition of larger plastic trash.

Microplastics have been discovered in a variety of organs, including the lungs, heart, blood, placenta, and feces, and have been ingested or inhaled by both humans and animals.

Ten million tonnes of these plastic fragments end up in the ocean, where they disperse as ocean spray and enter the atmosphere.

This revealed that microplastics had become a significant component of clouds, poisoning almost everything we eat and drink via “plastic rainfall.”

While much study on microplastics has focused on aquatic ecosystems, few studies have looked into how they affect cloud formation and climate change as “airborne particles.”

A team of Japanese scientists led by Hiroshi Okochi, a Professor at Waseda University, researched the path of airborne microplastics (AMPs) as they circulate in the biosphere, endangering human health and the climate.

Their findings were recently published in the journal Environmental Chemistry Letters, with contributions from co-authors Yize Wang of Waseda University and Yasuhiro Niida of PerkinElmer Japan Co. Ltd.

“Microplastics in the free troposphere are transported and contribute to global pollution. If the issue of ‘plastic air pollution’ is not addressed proactively, climate change and ecological risks may become a reality, causing irreversible and serious environmental damage in the future,” explained Okochi.

To investigate the role of these tiny plastic particles in the troposphere and the atmospheric boundary layer, the team collected cloud water from the summit of Mount Fuji, the south-eastern foothills of Mt. Fuji (Tarobo), and the summit of Mt. Oyama – regions at altitudes ranging between 1300-3776 meters.

Using advanced imaging techniques like attenuated total reflection imaging and micro-Fourier transform infrared spectroscopy (µFTIR ATR imaging), the researchers determined the presence of microplastics in the cloud water and examined their physical and chemical properties.

They identified nine different types of polymers and one type of rubber in the AMPs detected.

Notably, most of the polypropylene that was detected in the samples was degraded and had carbonyl (C=O) and/or hydroxyl (OH) groups. The Feret diameters of these AMPs ranged between 7.1 – 94.6 µm, the smallest seen in the free troposphere. Moreover, the presence of hydrophilic (water-loving) polymers in the cloud water was abundant, suggesting that they were removed as “cloud condensation nuclei.” These findings confirm that AMPs play a key role in rapid cloud formation, which may eventually affect the overall climate.