Galea Jack, Agius Anastasi Anthea, Vella Daniel A, Briffa Sophie M
Department of Metallurgy and Materials Engineering, Faculty of Engineering, University of Malta, Msida MSD 2080, Malta.
ACS Omega. 2025 Aug 12;10(33):37486-37494. doi: 10.1021/acsomega.5c03491. eCollection 2025 Aug 26.
During their lifetime, microplastics undergo transformations and react in ways that change their behavior and properties over time. Current standard plastic weathering protocols, which were developed prior to the increased concern about plastic pollution, may not be fully suited for microplastic studies as they aim to monitor durability and understand bulk plastic behavior, with little concern about fragments or leachates produced during degradation. This work aims to age poly-(ethylene terephthalate) (PET) microplastics (MPs) in a custom-built weathering chamber replicating Mediterranean shoreline conditions (detailed in the authors' previous work). This work studies the physicochemical changes of PET microplastic pellets (3-5 mm) following aging for a period of 90 days in dry and aquatic environments within a purposely designed weathering chamber. The chamber implemented UV-A, mechanical abrasion, and elevated temperatures to replicate the shore conditions. Micro-Raman spectroscopy was used to follow changes in the carbonyl content, crystallinity, and phenyl content of the PET MPs. Additionally, scanning electron microscopy (SEM) paired with energy-dispersive spectroscopy (EDS) was used to observe changes at the surface of the aged PET MPs. SEM showed that abrasion led to surface roughening and fibrillation. Despite changes being noted, no clear pattern emerged within the processed Raman spectroscopic results to elicit the contributions of UV radiation, salinity, and temperature. Loss of the surface layer by fragmentation and exposure of new surfaces could explain the fluctuating micro-Raman data. This work demonstrates early-stage degradation features including fluctuating chemical changes, fragmentation, abrasion, and salt crystallization under environmentally realistic Mediterranean shoreline conditions while laying methodological groundwork for future microplastic weathering research that seeks longer durations.
在其生命周期内，微塑料会发生转变并以随时间改变其行为和特性的方式发生反应。当前的标准塑料老化试验方法是在对塑料污染关注度提高之前制定的，可能并不完全适用于微塑料研究，因为它们旨在监测耐久性并了解块状塑料的行为，而很少关注降解过程中产生的碎片或渗滤液。这项工作旨在在一个定制的老化试验箱中对聚对苯二甲酸乙二酯（PET）微塑料进行老化处理，该试验箱模拟地中海海岸线条件（作者之前的工作中有详细描述）。这项工作研究了在专门设计的老化试验箱中，PET微塑料颗粒（3 - 5毫米）在干燥和水生环境中老化90天后的物理化学变化。该试验箱采用紫外线A、机械磨损和升高温度来模拟海岸条件。利用显微拉曼光谱跟踪PET微塑料中羰基含量、结晶度和苯基含量的变化。此外，扫描电子显微镜（SEM）与能量色散光谱（EDS）相结合，用于观察老化后的PET微塑料表面的变化。扫描电子显微镜显示磨损导致表面粗糙和原纤化。尽管观察到了变化，但在处理后的拉曼光谱结果中没有出现明确的模式来确定紫外线辐射、盐度和温度的影响。表面层因破碎而损失以及新表面的暴露可以解释拉曼显微数据的波动。这项工作展示了在环境真实的地中海海岸线条件下的早期降解特征，包括化学变化波动、破碎、磨损和盐结晶，同时为未来寻求更长持续时间的微塑料老化研究奠定了方法基础。
