Rapid disinfection byproduct formation from microplastics-derived dissolved organic matter during short-term chlorination: Polymer-dependent pathways

Microplastics-derived dissolved organic matter (MPs-DOM) has emerged as a potential precursor of disinfection byproducts (DBPs), yet its behavior under realistic short-term chlorination remains poorly understood. Here, we investigated the formation patterns of both conventional and unknown DBPs from polystyrene (PS) and polyethylene terephthalate (PET) leachates under short contact times, combining bulk DBP analysis with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Abundant traditional DBPs were formed rapidly, with trihalomethanes (THMs) as the dominant species. In comparison, PS-DOM showed higher chlorine consumption but PET-DOM produced higher DBP yields and a broader spectrum of species, accounting for 14.63 µg/mg DOC of total 15 DBPs subtypes versus 8.56 µg/mg DOC of total 12 DBPs subtypes for 60 min. For unknown DBPs, molecular-level analysis revealed that PET-DOM generated a more diverse pool of DBPs enriched in oxidized compounds, whereas DBPs derived from PS-DOM were relatively more unsaturated and aromatic-like. Further analysis reflect distinct transformation for two DOM during chlorination. PS-DOM underwent decarbonization, and mono-halogenation dominated its DBP formation. In contrast, PET-DOM exhibited oxidation transformation, with mono- and multi-halogenation contributing comparably to DBP formation. These findings demonstrate that DBP formation from MPs-DOM is highly dependent on polymer structure and can occur rapidly under short-term chlorination. And the elevated DBP formation potential of PET-DOM highlights a greater risk of PET MPs in aquatic environments.