Scientists reveal how microplastics release invisible chemical clouds into waterways

Researchers have discovered that microplastics floating in rivers, lakes, and oceans continuously leak a complex mixture of dissolved organic chemicals that evolve over time, especially under sunlight. The work provides the most detailed molecular-level view to date of how this microplastic-derived dissolved organic matter, or MPs DOM, forms and transforms in natural waters.

The study, published in New Contaminants, compared four major plastic types with natural dissolved organic matter from rivers. Using kinetic modeling, fluorescence spectroscopy, high-resolution mass spectrometry, and infrared analysis, the scientists showed that each type of plastic produces a distinct chemical fingerprint that changes as sunlight breaks down polymer surfaces.

“Microplastics do not just pollute aquatic environments as visible particles. They also create an invisible chemical plume that changes as they weather,” said lead author Jiunian Guan of Northeast Normal University. “Our study shows that sunlight is the primary driver of this process, and that the molecules released from plastics are very different from those produced naturally in rivers and soils.”

Sunlight accelerates the release of plastic associated carbon

The researchers exposed polyethylene, polyethylene terephthalate, polylactic acid, and polybutylene adipate co terephthalate microplastics to water under dark and ultraviolet conditions for up to 96 hours. Sunlight dramatically increased the rate at which all plastics released dissolved organic carbon. Biodegradable plastics such as PLA and PBAT released the most, reflecting their more fragile chemical structures.

Using kinetic models, the team found that the release followed zero order behavior, meaning the process was controlled by physical and chemical constraints at the plastic surface rather than by the concentration of material already in the water. Film diffusion was identified as the rate limiting step under ultraviolet light.

A chemically rich mix of additives, monomers, and oxidized fragments

Advanced spectroscopy and mass spectrometry revealed that MPs DOM contains a diverse set of molecules originating from additives, monomers, oligomers, and photo oxidized fragments. Aromatic plastics such as PET and PBAT produced particularly complex mixtures.

As plastics weathered, oxygen containing functional groups increased, indicating the formation of alcohols, carboxylates, ethers, and carbonyls. Additives such as phthalates also appeared, consistent with their weak bonding within polymer matrices.

Fluorescence analyses demonstrated that MPs DOM resembled material produced by microbial activity rather than by terrestrial sources, in sharp contrast to natural dissolved organic matter. Over time, the chemical composition shifted, with relative contributions of protein like, lignin like, and tannin like substances changing depending on polymer type and sunlight exposure.

Environmental impacts could intensify as plastic pollution grows

The evolving chemical mixtures released from microplastics could influence aquatic ecosystems in several ways. MPs DOM is generally composed of small, bioavailable molecules that may stimulate or inhibit microbial activity, alter nutrient cycling, or interact with metals and pollutants. Previous studies have shown that MPs DOM can generate reactive oxygen species, affect disinfection byproduct formation, and modify pollutant adsorption.

“Our findings highlight the importance of considering the full life cycle of microplastics in water, including the invisible dissolved chemicals they release,” said co author Shiting Liu. “As global plastic production continues to rise, these dissolved compounds may have growing environmental significance.”

Toward predictive tools for plastic pollution chemistry

Given the complexity of MPs DOM and its dynamic nature, the team suggests that machine learning approaches could help predict how this material evolves in the environment. Future models could support risk assessments related to aquatic health, contaminant behavior, and carbon cycling.

The authors note that microplastic inputs to rivers and oceans remain largely uncontrolled. As plastics continue to fragment and weather under sunlight, the release of MPs DOM is expected to intensify, making it essential to understand its chemical behavior across different stages of degradation.

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Journal reference: Liu S, Zelang X, Ma C, Li Z, Wang X, et al. 2025. Molecular-level insights into derivation dynamics of microplastic-derived dissolved organic matter. New Contaminants 1: e016 

https://www.maxapress.com/article/doi/10.48130/newcontam-0025-0016 

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About the Journal:

New Contaminants is an open-access journal focusing on research related to emerging pollutants and their remediation.

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