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Aging of microplastics increases their adsorption affinity towards organic contaminants
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Researchers found that microplastics that have been weathered by sunlight and environmental exposure absorb significantly more chemical pollutants than fresh microplastics, with up to a 4.7-fold increase in adsorption. Ultraviolet exposure changes the surface chemistry of the plastics, making them stickier for contaminants. This matters because most microplastics in nature are weathered, meaning they may be carrying more toxic chemicals into the food chain than laboratory studies using new plastics would suggest.
When released in the environment, microplastics undergo surface weathering due to mechanical abrasion and ultraviolet exposure. In this study, the adsorption of two model contaminants, phenanthrene and methylene blue, by weathered high density polyethylene (HDPE) and polypropylene (PPE) was evaluated to understand how the microplastics' aging influences contaminant adsorption. Microplastics were aged through an accelerated weathering process using ultraviolet exposure with or without hydrogen peroxide. Adsorption isotherms were conducted for both contaminants on pristine and aged microplastics. The adsorption of organic contaminants was higher on aged microplastics than on pristine ones, with methylene blue having the highest affinity increase with aging at 4.7-fold and phenanthrene having a 1.9-fold increase compared to the pristine particles. To understand the mechanisms involved with higher adsorption of contaminants by aged microplastics, changes in the specific surface area and surface chemistry of aged microplastics were characterized by Fourier Transform Infrared Spectroscopy, X-ray Photoelectron Spectroscopy, zeta potential, X-ray tomography, and Brunauer-Emmett-Teller krypton adsorption analyses. The results of this study show that oxidation of microplastics can enhance the adsorption of organic contaminants, which may increase their role as vectors of contaminants in the aquatic food chain.
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Simultaneous sorption behaviors of UV filters on the virgin and aged micro-high-density polyethylene under environmental conditions.
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Researchers studied how UV filter chemicals from sunscreens adsorb onto both virgin and aged high-density polyethylene microplastics. They found that aged, weathered microplastics had greater capacity to accumulate UV filter compounds than fresh plastic due to changes in surface chemistry. This suggests that environmental aging of plastics increases their ability to transport chemical contaminants.
Effect of sunlight aging on physicochemical properties and sorption capacities of environmental microplastics: implications for contamination by PAHs
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Researchers studied how sunlight aging changes the physical and chemical properties of three common plastics -- polyethylene, polypropylene, and polystyrene -- and their ability to absorb pollutants. They found that plastics exposed to outdoor sunlight for 69 days absorbed up to 3.5 times more of the carcinogenic compound pyrene compared to new plastics, likely due to surface changes from weathering. The findings suggest that older, weathered microplastics in the environment may accumulate harmful pollutants more readily than fresh plastic particles.
Weathering effect triggers the sorption enhancement of microplastics against oxybenzone
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Researchers found that weathering in air, seawater, and freshwater makes PET microplastics absorb significantly more oxybenzone, a common sunscreen chemical, than fresh plastic does. Aging creates surface cracks and new chemical groups that increase the plastic's ability to bind pollutants. The study suggests that as microplastics weather in the environment, they become more effective carriers of harmful chemicals.
Surface characteristics and adsorption properties of polypropylene microplastics by ultraviolet irradiation and natural aging
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This study examined how aging and UV light change the surface properties of polypropylene microplastics and their ability to absorb other pollutants. UV-aged microplastics absorbed significantly more of a common dye pollutant, while naturally aged particles absorbed less due to biological film buildup. Understanding how microplastics change over time in the environment matters because aged particles may carry different levels of harmful chemicals than fresh ones.
Yellowing, Weathering and Degradation of Marine Pellets and Their Influence on the Adsorption of Chemical Pollutants
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Plastic pellets collected from marine environments were found to yellow and degrade over time due to UV exposure and weathering, and this aging process increases their ability to adsorb persistent organic pollutants. Weathered microplastics can therefore carry a higher chemical load of toxic contaminants compared to fresh plastic. This has implications for marine organisms that ingest aged plastic particles, as they may be exposed to concentrated cocktails of harmful chemicals.
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