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Hydrophilic Fraction of Dissolved Organic Matter Largely Facilitated Microplastics Photoaging: Insights from Redox Properties and Reactive Oxygen Species
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This study investigated how dissolved organic matter in natural water affects the breakdown of microplastics by sunlight. The water-soluble fraction of organic matter was most effective at speeding up microplastic aging by generating reactive oxygen species that attack the plastic surface. This matters because faster breakdown of microplastics in the environment creates smaller, potentially more dangerous nanoplastic particles that can more easily enter living organisms.
Dissolved organic matter (DOM) exists widely in natural water, which inevitably influences microplastic (MP) photoaging. Nevertheless, the impacts of DOM fractions with diverse molecular structures on MP photoaging remain to be elucidated. This study explored the photoaging mechanisms of polylactic acid (PLA)-MPs and polystyrene (PS)-MPs in the presence of DOM and its subfractions (hydrophobic acid (HPOA), hydrophobic neutral (HPON), and hydrophilic (HPI)). Across DOM fractions, HPI exhibited the highest electron accepting capacity (23 μmol e- (mg C)-1) due to its abundant tannin-like species (36.8%) with carboxylic groups, which facilitated more reactive oxygen species generation (particularly hydroxyl radical), leading to the strongest photoaging rate of two MPs by HPI. However, the sequences of bond cleavage during photoaging of each MPs were not clearly shifted as revealed by two-dimensional infrared correlation spectra. Inconspicuous effects on the extent of PS- and PLA-MPs photoaging were observed for HPOA and HPON, respectively. This was mainly ascribed to the occurrence of inhibitory mechanisms (e.g., light-shielding and quenching effect) counteracting the reactive oxygen species-promoting effects. The findings identified the HPI fraction of DOM for promoting PS- and PLA-MPs photoaging rate and first constructed a link among DOM molecular structures, redox properties, and effects on MP photoaging.
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Molecular Weights of Dissolved Organic Matter Significantly Affect Photoaging of Microplastics
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This study found that dissolved organic matter in natural water significantly speeds up how quickly microplastics break down under sunlight, with smaller organic molecules having the strongest effect. The breakdown process generates reactive chemical species that attack the plastic surfaces. This is important because it means microplastics in natural waters may fragment into smaller, potentially more harmful nanoplastics faster than lab studies using pure water would suggest.
Dissolved Organic Matter Enhanced the Aggregation and Oxidation of Nanoplastics under Simulated Sunlight Irradiation in Water
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Dissolved organic matter was found to enhance both the aggregation and photooxidation of nanoplastics under simulated sunlight in water, with humic substances promoting particle clustering and accelerating surface oxidation. The results indicate that organic matter content in natural waters strongly influences nanoplastic fate and transformation.
Opposite impact of DOM on ROS generation and photoaging of aromatic and aliphatic nano- and micro-plastic particles.
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This study examined how dissolved organic matter (DOM) in water affects the photodegradation and reactive oxygen species (ROS) generation of aromatic versus aliphatic plastic particles. Researchers found that DOM had opposite effects on the two types of plastics, enhancing aging of aromatic polymers while inhibiting aging of aliphatic ones. The results reveal that natural water chemistry plays a complex role in determining how quickly different microplastics break down.
Significant contribution of different sources of particulate organic matter to the photoaging of microplastics
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Researchers discovered that particulate organic matter from different natural sources can significantly accelerate the aging of microplastics when exposed to UV light. Organic matter from peat soil showed the strongest effect, generating reactive oxygen species that broke down plastic surfaces more quickly. The study suggests that natural organic matter in the environment plays a larger role in microplastic degradation than previously recognized.
Photoaging mechanism of microplastics: a perspective on the effect of dissolved organic matter in natural water
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This perspective paper examines how microplastics in natural water photoage under UV irradiation via reactive oxygen species generation, breaking down polymer bonds, and explores how dissolved organic matter may accelerate or alter these aging pathways. Understanding photoaging is critical because it fragments plastics into smaller and more biologically available nanoplastics while releasing toxic chemical additives into aquatic ecosystems.
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