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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.
Chemical degradation testing often involves monitoring the loss of a chemical or the evolution of a single diagnostic product through time. Here, we demonstrate a novel approach to tracing complex degradation networks using mass-spectrometry-based methods and open cheminformatics tools. Ester- and ether-based thermoplastic polyurethane (TPU_Ester and TPU_Ether) microplastics (350 μm) and microplastics-derived dissolved organic carbon (MP-DOC) were photoweathered in a simulated marine environment and subsequently analyzed by liquid chromatography coupled to high-resolution mass spectrometry. We formula-annotated 1342 and 2344 unique features in the MP-DOC of TPU_Ester and TPU_Ether, respectively. From these, we extracted 199 and 568 plausible parent-transformation product pairs via matching of features (a) with complementary increasing and decreasing trends (Spearman's correlation coefficient between normalized intensity and time), (b) spectral similarities of at least three accurate mass MS2 fragments, and (c) at least 3 ppm agreement between the theoretical and measured change in m/z between the parent-transformation product formula. Molecular network analysis revealed that both chain scission and cross-linking reactions occur dynamically rather than degradation proceeding in a monotonic progression to smaller or more oxygenated structures. Network nodes with the highest degree of centrality were tentatively identified using in silico fragmentation and can be prioritized for toxicity screening or other physicochemical properties of interest. This work has important implications for chemical transformation tracking in complex mixtures and may someday enable improved elucidation of environmental transformation rules (i.e., structure-reactivity relationships) and fate modeling.
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Molecular fingerprints of dissolved organic matter leached from microplastics over prolonged photochemical aging: Implications for aquatic carbon cycling
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Researchers used ultra-high-resolution mass spectrometry to identify the dissolved organic molecules that leach from polypropylene, polyethylene, and polystyrene microplastics after prolonged exposure to sunlight. They found that polystyrene released the most diverse array of molecules, many of which could persist in water systems. The study suggests that as microplastics degrade in sunlight, they release non-natural organic compounds that may affect the aquatic carbon cycle from rivers to oceans.
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.
High-Resolution Mass Spectrometry Combined with Reactive Oxygen Species Reveals Differences in Photoreactivity of Dissolved Organic Matter from Microplastic Sources in Aqueous Environments
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Researchers analyzed the dissolved organic matter that different types of microplastics release into water and how it reacts with sunlight. Plastics with aromatic structures like polystyrene and PET released compounds that broke down faster and generated more reactive oxygen species than polyethylene or polypropylene. Understanding how different plastics chemically alter water quality is important because these released compounds and reactive species can affect aquatic life and the safety of water sources used by people.
Sizeand Structure-DependentMolecular FingerprintTransformation of Microplastic-Derived Dissolved Organic Matter inSunlit Seawater: Implication for Marine Carbon Cycles
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Researchers investigated how the size and structure of microplastics influence the photochemical transformation of microplastic-derived dissolved organic matter in sunlit seawater, finding that inherent polymer properties shape the molecular fingerprint changes with implications for marine carbon cycling.
Sizeand Structure-DependentMolecular FingerprintTransformation of Microplastic-Derived Dissolved Organic Matter inSunlit Seawater: Implication for Marine Carbon Cycles
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Researchers investigated how the size and structure of microplastics influence the photochemical transformation of microplastic-derived dissolved organic matter in sunlit seawater, finding that inherent polymer properties shape the molecular fingerprint changes with implications for marine carbon cycling.
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