Microplastics aged in various environmental media exhibited strong sorption to heavy metals in seawater

To date, the degradation of microplastics (MPs; <5 mm) in different environments, particularly their adsorption characteristics for coexisted metal pollutants remains to be elucidated. Thus, this study investigated the effects of aging MPs, including polyamide (mPA), polyethylene terephthalate (mPET), polystyrene (mPS), and polyvinyl chloride (mPVC) for 3 months under UVA irradiation in four environmental media (air, seawater, sand, and soil) and adsorption of heavy metals (Cu, Cd) onto seawater-aged mPS and mPVC. The results showed that surface morphological changes, including cracks, oxidized particles, and wrinkles, appeared on aged MPs. The heavy metal adsorption capacity decreased in the order aged mPVC > aged mPS > unaged mPS > unaged mPVC, and the Cu²⁺ and Cd²⁺ ions competed for active adsorption sites on the MPs surfaces. Overall, the aging environment affected the physical and chemical properties of MPs and the aging of MPs enhanced their adsorption of coexisting metals tested.