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Effect of sunlight aging on physicochemical properties and sorption capacities of environmental microplastics: implications for contamination by PAHs
Summary
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.
This study investigates the effects of ultraviolet (UV) aging on the physicochemical properties and adsorption capacity of three plastics commonly detected in the environment: polyethylene (PE), polypropylene (PP), and polystyrene (PS). One set of plastic samples was exposed to Xe-based simulated sunlight for up to 5 days and another set to outdoor conditions for up to 69 days. The physicochemical properties and ability of the pristine and aged plastic particles to adsorb pyrene, a representative polycyclic aromatic hydrocarbon (PAH), are evaluated. For the outdoor-exposed PP and PS samples, distinct Fourier transform infrared peaks related to carbonyl groups are detected. The adsorption coefficients of pyrene after 72 h of agitation in PE and PP samples aged via 69 days of outdoor exposure are 2.9 and 3.5 times higher compared with that in the respective pristine samples. This increase in adsorption capacity is probably attributed to these plastics undergoing changes in surface properties, including embrittlement. The findings indicate that the accumulation of PAHs on microplastics is accelerated on aged material surfaces, emphasizing the need for further studies under conditions that simulate natural sunlight exposure.
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