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pH-Responsive leaching profiles from photodegradation of microplastics
Summary
Researchers systematically examined how UV photodegradation of microplastics triggers pH-dependent release of chemical additives, non-intentionally added substances, and oligomers under controlled degradation conditions, characterising leaching profiles across a range of plastic polymer types. The study identified that pH strongly governs which hazardous compounds leach from degrading plastics and at what concentrations, revealing a mechanism by which environmental conditions modulate chemical risk from microplastic pollution.
Over 13,000 chemicals are linked to plastics, including more than 3,200 with hazardous properties. Numerous non-intentionally added substances (NIAS), such as degradation products, processing aids, residual monomers, impurities in plastic additives, and transformation products, are present in varying amounts and are often not detected by instrumental target analysis. Despite the potential threat, plastic additives and oligomers are still mostly unregulated and under-researched, whereas the effect of different degradation mechanisms is scarcely investigated jointly. This study systematically investigated the photoaging behavior and mechanism of PLA MPs in aquatic environment and in different pHs, employing a liquid chromatography−high-resolution mass-spectrometry (LC−HRMS) instrumentation. Specifically, different pH values were selected and applied in aquatic media combined with UV irradiation, in order to investigate the degradation behavior in the environment. Two approaches were exploited for the treatment of the acquired data; suspect screening with an in-house database based on bibliography, and non-target analysis with a customized workflow. The acquired data were subjected to peak picking and integration, retention time alignment, peak and compound grouping, and background subtraction and filtering strategies. Compound annotation with in-house and online spectral databases (mzCloud) enabled the tentative identification of several potential migrants in aging simulants with high confidence based on fragmentation pattern and isotopic profile, some of which were also reported as NIAS. Results showed alterations at the additives and leachates release profiles in accordance with leaching time and pH values. Overall, the analytical and leaching methods described here provide new tools to study plastic leachates and evaluate their leaching in environmentally relevant matrices. These methods can inform monitoring, threat assessment, and future regulatory efforts Acknowledgement This research has been funded by the Region of Central Macedonia through the action Ïnvestment Innovation Plansb̈y (NSRF 2014-2020), with the acronym AutopHECametro, under the Project No ΚΜΡ6-0290626, and it is gratefully acknowledged. Also see: https://micro2024.sciencesconf.org/559575/document