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Abstract
Polyethylene glycols (PEGs), a major class of water-soluble polymers (WSPs), are widely used in diverse applications which may lead to their release into the environment. This work investigates the reaction of PEGs with photochemically produced hydroxyl radicals (•OH), an important environmental oxidant, and assesses the effect of reaction-induced molecular weight (MW) decreases on PEG biodegradation dynamics in soil and sediment. Probabilistic kinetic modelling revealed a significant reduction in PEG MW after only a few •OH-induced chain scissions on initial PEG molecules. The simulation results were experimentally validated by reacting 13C-labeled PEGs (average MW = 6200 Da) with photochemically produced •OH, resulting in pronounced shifts in the size distribution of PEGs towards lower MWs with increasing reaction extents. Incubations of the initial non-reacted and three incrementally •OH-reacted PEG mixtures over a 150-day period in sediment and soil demonstrated increasing rates and extents of PEG biodegradation to 13CO2 with increasing •OH-reaction extent and thus decreasing PEG average MW. This study underscores the importance of considering the MW distributions of WSPs and their dynamic changes through biotic or abiotic chain scission reactions — showcased herein by reacting PEGs with photochemically produced •OH — in mechanistically understanding WSP biodegradability in natural and engineered receiving environments.
Supplementary materials
Title
Supplementary Information
Description
This Supplementary Information provides additional details supporting the findings presented in the manuscript titled "Photochemical Chain Scissions Enhance Polyethylene Glycol Biodegradability: From Probabilistic Modelling to Experimental Demonstration." It includes data and methods related to the Monte Carlo simulations, analytical techniques, and experimental setup.
Section S1 describes the rate constants used in Monte Carlo simulations, detailing the relationship between the degree of polymerization and hydroxyl radical reaction rates. Section S2 presents the analytical methodologies, including HPLC-CAD, HR-MS, and 13C NMR, used for characterizing PEG degradation products. Section S3 provides the properties of the soil used in biodegradation experiments. Section S4 details the automated incubation setup for monitoring PEG mineralization via cavity ring-down spectroscopy. Finally, Section S5 outlines the quantification of residual PEG-derived carbon in soil and sediment post-incubation using EA-IRMS.
Figures S1-S5 provide visual representations of key experimental data, complementing the main text.
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