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Differential photoaging behaviors of different colored commercial polyethylene microplastics in water: The important role of color characteristics

The Science of The Total Environment 2024 18 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Xing Li, Daofen Huang, Daofen Huang, Haoran Dong, Jia Wen, Jie Dong, Chang Zhang, Long Li, Haoxuan Zhang

Summary

Researchers compared the photoaging behavior of transparent and five differently colored commercial polyethylene microplastics under UV exposure. They found that transparent microplastics degraded fastest, followed by yellow and red, while blue and green were most resistant, with the pattern correlating to color wavelength, lightness, and saturation characteristics. The findings demonstrate that color plays an important and previously overlooked role in determining how quickly microplastics break down in the environment.

Polymers

Upon entering the environment, plastics would undergo photoaging and forming microplastics (MPs). However, information on the photoaging behavior of colored MPs and how the color characteristics (wavelength, lightness, and saturation) influence their photoaging process is still lacking. Thus, attention was paid to comparing the photoaging process of transparent and five-colored MPs. To reveal the degree of photodegradation and photooxidation, physicochemical changes (e.g., surface morphology, functional groups, and the leaching of intermediates) of transparent and five-colored MPs were explored. Photodegradation rates and photooxidation degrees ranked transparent > yellow > red ≈ orange > green > blue. However, transparent and five-colored MPs exhibited a different photoaging sequence and eluted different photodegradation products from each other. Pearson correlation analysis was used to describe the relationships between color characteristics (wavelength, lightness, and saturation) and their photoaging properties, and the results indicated that MPs (yellow, red, and orange) with longer color wavelength, higher lightness, and lower saturation are more susceptible to UV light than MPs with shorter color wavelength, lower lightness and higher saturation (green and blue). The findings demonstrate that the photoaging process of colored MPs is correlated to their color characteristics, highlighting the important role of color in MPs' environmental fate.

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