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Photochemical weathering of polyurethane microplastics produced complex and dynamic mixtures of dissolved organic chemicals
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Researchers studied how sunlight breaks down polyurethane microplastics in ocean surface waters and what chemical byproducts are released. The study found that photochemical weathering produced complex and constantly changing mixtures of dissolved organic chemicals, with different polyurethane types releasing different compounds. The findings reveal that while sunlight helps degrade microplastics, the resulting chemical cocktails may themselves pose environmental risks.
Sunlight exposure can naturally mitigate microplastics pollution in the surface ocean, however it results in emissions of dissolved organic carbon (DOC) whose characteristics and fate remain largely unknown. In this work, we investigated the effects of solar radiation on polyether (TPU_Ether) and polyester (TPU_Ester) thermoplastic polyurethane, and on a thermoset polyurethane (PU_Hardened). The microplastics were irradiated with simulated solar light with a UV dose of 350 MJ m-2, which corresponds to roughly 15 months outdoor exposure at 31° N latitude. The particles were characterized using ATR-FTIR and elemental analysis. The DOC released to the aqueous phase was quantified by total organic carbon analysis and characterized by nontarget liquid chromatography coupled to high-resolution mass spectrometry. Polyurethane microplastics were degraded following mechanisms reconcilable with UV photo-oxidation. The carbon mass fraction released to the aqueous phase was 8.5 ± 0.5%, 3.7 ± 0.2%, and 2.8 ± 0.2% for TPU_Ether, TPU_Ester, and PU_Hardened, respectively. The corresponding DOC release rates, expressed as mg carbon per UV dose were 0.023, 0.013, and 0.010 mg MJ-1 for TPU_Ether, TPU_Ester and PU_Hardened, respectively. Roughly three thousand unique by-products were released from photo-weathered TPUs, whereas 540 were detected in the DOC of PU_Hardened. This carbon pool was highly complex and dynamic in terms of physicochemical properties and susceptibility to further photodegradation after dissolution from the particles. Our results show that plastics photodegradation in the ocean requires chemical assessment of the DOC emissions in addition to the analysis of aged microplastics and that polymer chemistry influences the chain scission products.
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Researchers incubated polyethylene, polypropylene, and expanded polystyrene microplastics in sunlit seawater and characterized the dissolved organic matter produced as the plastics broke down. The study found that sunlight generated hundreds of unique oxygen-containing chemical products from each plastic type, while virtually none were produced in the dark. Evidence indicates that a single process, photodegradation, can transform simple plastic polymers into a complex array of dissolved organic chemicals in ocean environments.
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This study investigated how ultraviolet light breaks down polystyrene microplastics and releases dissolved organic matter, including plastic additives, into the surrounding water. Greater UV exposure produced more complex chemical mixtures with higher levels of potentially toxic compounds. The findings are important because sunlight-driven breakdown of microplastics in the environment may release harmful chemicals into water sources that people use for drinking and recreation.
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Researchers investigated the molecular-level changes that occur when polystyrene microplastics break down under light exposure and release dissolved organic matter into water. They found that the released molecules were highly diverse and changed dynamically over the course of aging, with different chemical classes appearing at different stages. The study provides new insight into how degrading microplastics introduce complex mixtures of organic chemicals into aquatic environments.
Understanding visible light and microbe-driven degradation mechanisms of polyurethane plastics: Pathways, property changes, and product analysis
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Tracking Dynamic Chemical Reactivity Networks with High-Resolution Mass Spectrometry: A Case of Microplastic-Derived Dissolved Organic Carbon
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Researchers developed a new method using high-resolution mass spectrometry to track how microplastics made of polyurethane break down into thousands of chemical byproducts when exposed to simulated sunlight in seawater. They found that degradation does not simply break plastics into smaller pieces but creates a complex web of chemical reactions producing many different organic compounds. This is important because these dissolved chemical byproducts from microplastic breakdown could have their own toxic effects on marine life and potentially enter the human food chain.
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