Photochemical weathering of polyurethane microplastics produced complex and dynamic mixtures of dissolved organic chemicals
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d2em00415a.pdf
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Published version
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Author(s)
Albergamo, Vittorio
Wohlleben, Wendel
Plata, Desirée L
Date Issued
January 24, 2023
Journal
Environmental Science: Processes & Impacts
Publisher
Royal Society of Chemistry (RSC)
Citation
Albergamo, Vittorio, Wohlleben, Wendel and Plata, Desirée L. 2023. "Photochemical weathering of polyurethane microplastics produced complex and dynamic mixtures of dissolved organic chemicals." Environmental Science: Processes & Impacts.
Version
Final published version
Abstract
Sunlight exposure can naturally mitigate microplastics pollution in the surface ocean, however it results in
emissions of dissolved organic carbon (DOC) whose characteristics and fate remain largely unknown. In
this work, we investigated the effects of solar radiation on polyether (TPU_Ether) and polyester
(TPU_Ester) thermoplastic polyurethane, and on a thermoset polyurethane (PU_Hardened). The
microplastics were irradiated with simulated solar light with a UV dose of 350 MJ m−2
, which corresponds
to roughly 15 months outdoor exposure at 31° N latitude. The particles were characterized using ATRFTIR and elemental analysis. The DOC released to the aqueous phase was quantified by total organic
carbon analysis and characterized by nontarget liquid chromatography coupled to high-resolution mass
spectrometry. Polyurethane microplastics were degraded following mechanisms reconcilable with UV
photo-oxidation. The carbon mass fraction released to the aqueous phase was 8.5 ± 0.5%, 3.7 ± 0.2%,
and 2.8 ± 0.2% for TPU_Ether, TPU_Ester, and PU_Hardened, respectively. The corresponding DOC
release rates, expressed as mg carbon per UV dose were 0.023, 0.013, and 0.010 mg MJ−1 for TPU_Ether,
TPU_Ester and PU_Hardened, respectively. Roughly three thousand unique by-products were released
from photo-weathered TPUs, whereas 540 were detected in the DOC of PU_Hardened. This carbon pool
was highly complex and dynamic in terms of physicochemical properties and susceptibility to further
photodegradation after dissolution from the particles. Our results show that plastics photodegradation in
the ocean requires chemical assessment of the DOC emissions in addition to the analysis of aged
microplastics and that polymer chemistry influences the chain scission products.
MIT Department
Massachusetts Institute of Technology. Department of Civil and Environmental Engineering
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Creative Commons Attribution NonCommercial License 3.0
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DOI of Published Version
https://doi.org/10.1039/d2em00415a
