Nanoplastics Weathering and Polycyclic Aromatic Hydrocarbon Mobilization

Despite increasing efforts to recycle plastic materials, large quantities of plastics waste continue to accumulate in the oceans. Persistent mechanical and photochemical degradation of plastics in the oceans yields micro- and nanoscale plastic particles, which represent potential vectors for mobilizing hydrophobic carcinogens in an aqueous milieu. Yet, the fate and potential threats associated with plastics remain largely unexplored. Herein, we apply an accelerated weathering protocol to consumer plastics to characterize the effect of photochemical weathering on the size, morphology, and chemical composition of nanoplastics under defined conditions and validate that the photochemical degradation is consistent with plastics harvested from the Pacific Ocean. Machine learning algorithms trained with accelerated weathering data successfully classify weathered plastics from nature. We demonstrate that photodegradation of poly(ethylene terephthalate) (PET)-containing plastics produces enough CO₂ to induce a mineralization process that results in the deposition of CaCO₃ on nanoplastics. Finally, we determine that despite UV-radiation induced photochemical degradation and mineral deposition, nanoplastics retain their ability to sorb, mobilize, and increase bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) in water and under simulated physiological gastric and intestinal conditions.