This microplastic-derived dissolved organic matter (MPs-DOM) differs fundamentally from natural organic matter in water and may alter microbial activity, pollutant behavior, and carbon cycling across aquatic ecosystems.
Microplastics are now ubiquitous in surface waters worldwide, often reaching concentrations of thousands of particles per liter. Over time, prolonged contact with water and exposure to sunlight causes plastics to leach dissolved organic compounds, collectively known as MPs-DOM. In heavily polluted surface waters, this material can contribute up to 10% of dissolved organic carbon (DOC) in the surface microlayer. Unlike natural organic matter (NOM), which originates from plants and soils, MPs-DOM is anthropogenic and enriched in low-molecular-weight, highly reactive compounds. Despite its growing presence, most studies have focused only on the initial or final states of MPs-DOM, leaving the dynamic processes governing its formation and transformation largely unexplored.
A study (DOI:10.48130/newcontam-0025-0016) published in New Contaminants on 05 December 2025 by Jiunian Guan’s team, Northeast Normal University, implies that microplastics influence ecosystems not only as particles, but also as dissolved chemical agents.
Using controlled leaching experiments, the study systematically compared dissolved organic matter released from four representative microplastics—polyethylene (PE), polyethylene terephthalate (PET), polylactic acid (PLA), and polybutylene adipate-co-terephthalate (PBAT)—with that derived from NOM under dark and UV-irradiated conditions. DOC release was quantified over time and interpreted using zero-order and pseudo-second-order kinetic models, together with intraparticle diffusion and Boyt analyses to identify rate-limiting steps. Chemical evolution during derivation was further characterized by FT-IR spectroscopy for functional groups, excitation–emission matrix fluorescence combined with PARAFAC for component dynamics and indices (FI, BIX, HIX), and ultrahigh-resolution FT-ICR-MS for molecular formulas, elemental classes, and van Krevelen-type compositional shifts. Under dark conditions, DOC increased steadily for both sources, but N-DOM released significantly more DOC than MPs-DOM, while biodegradable plastics released more DOC than conventional plastics. Kinetic and diffusion analyses indicated faster DOC derivation for N-DOM, with intraparticle diffusion limiting MPs-DOM release and film diffusion controlling N-DOM. Under UV irradiation, DOC derivation accelerated markedly, especially for biodegradable MPs, and zero-order kinetics remained valid, indicating a constant release rate governed by polymer properties and irradiation rather than concentration. Diffusion control shifted to film diffusion for both MPs-DOM and N-DOM, and DOCUV/DOCdark increased over time, with UV sensitivity ranked PBAT > PLA > PET > PE ≫ NOM, confirming UV light as the dominant driver of MPs-DOM formation. Spectroscopic analyses revealed that UV exposure promoted the release of polymer monomers, oligomers, and additives such as phthalates, alongside the formation of oxygen-containing functional groups via hydrolysis and photochemical reactions. Fluorescence analyses showed that MPs-DOM evolved from additive-dominated signatures toward more protein-like and low-molecular-weight humic-like components, whereas N-DOM remained terrestrially humic and comparatively stable. FT-ICR-MS further demonstrated polymer-specific molecular trajectories: PET-derived DOM became increasingly oxidized and aromatic, PLA-derived DOM shifted toward carbohydrate- and tannin-like compounds, and overall MPs-DOM followed distinct UV-driven pathways largely absent in natural DOM, highlighting its unique and dynamic role in sunlit aquatic carbon cycling.
The findings suggest that MPs-DOM is not merely an additional carbon source, but a chemically active agent capable of reshaping aquatic biogeochemistry. Its low molecular weight and oxidized nature make it highly bioavailable, potentially stimulating or inhibiting microbial growth and altering food-web dynamics. MPs-DOM can bind metals, influence mineral transformations, interfere with pollutant adsorption, and act as a precursor for disinfection byproducts in water treatment. Under sunlight, it can also generate reactive oxygen species, affecting contaminant degradation and nanoparticle formation.
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References
DOI
10.48130/newcontam-0025-0016
Original Source URL
https://doi.org/10.48130/newcontam-0025-0016
Funding information
This work was financially supported by the National Natural Science Foundation of China (42471089, 4231101419), the Research Foundation of the Science and Technology Agency (20250102178JC), and the Education Department of Jilin Province (JJKH20250337KJ).
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