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Contribution of free hydroxyl radical to the formation of micro(nano)plastics and release of additives during polyethylene degradation in water

Environmental Pollution 2023 13 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Yu Tang, Kaiqing Fan, Indika Herath, Williamson Gustave, Chuxia Lin, Junhao Qin, Rongliang Qiu

Summary

Researchers found that hydroxyl radicals generated from hydrogen peroxide in water significantly accelerate the degradation of polyethylene and the formation of micro- and nano-sized plastic particles. The study, conducted over 620 days, demonstrates that naturally occurring reactive oxygen species in aquatic environments may contribute to the generation and spread of secondary microplastics.

Polymers

The omnipresence of secondary microplastics (MPs) in aquatic ecosystems has become an increasingly alarming public health concern. Hydrogen peroxide (HO) is an important oxidant in nature and the most stable reactive oxygen species occurred in natural water. In order to explore the contribution of free ˙OH generated from HO-driven Fenton-like reactions on the degradation of polyethylene (PE) and generation of micro- and nano-scale plastics in water, a batch experiment was conducted over a period of 620 days in water treated with micromolar HO. The incorporation of HO in water induced the formation of flake-like micro(nano)-sized particles due to intensified oxidative degradation of PE films. The presence of ˙OH significantly enhanced the generation of both micro- and nano-scale plastics exhibiting a higher proportion of particles in the range of 200-500 nm compared to the Control. Total organic carbon in the HO treated solution was nearly 174-fold higher than that of the Control indicating a substantial liberation of organic compounds due to the oxidative degradation of native carbon chain of PE and subsequent decomposition of its additives. The highly toxic butylated hydroxytoluene detected from the gas chromatography-mass spectrometry (GC-MS) analysis implied the toxicological behavior of secondary micro(nano)plastics influenced by the oxidation and decomposition processes The findings from this study further expand our understanding of the role of ˙OH in degrading PE micro-scale plastics into nanoparticles as an implication of naturally occurring HO in aquatic environments. In the future, further attention should be drawn to the underlying mechanisms of HO-driven in-situ Fenton reaction mediated by natural environmental conditions targeting the alternation of light and darkness on the oxidative degradation of plastics.

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