Aging of mask microplastics in distinct environmental media: Impacts on pollutants adsorption and cross-media migration propensity

The extensive use of disposable surgical masks has led to the widespread release of mask microplastics (M-MPs) into the environment. M-MPs not only pose direct risks but also act as pollutant vectors by adsorbing contaminants, enhancing pollutant enrichment in ecosystems through food web transmission. However, the effects of aging pathways on the aging degree of M-MPs and their potential as contaminant carriers remain unclear. This study systematically compared M-MPs characteristics under different aging pathways including controlled UV irradiation, landfill leachate, outdoor air, pond water and soil and evaluated their adsorption behaviors. The main findings are as follows: (1) Landfill leachate caused the most severe aging (CI = 1.75 after 120 d), with an intensity three times greater than outdoor exposure; (2) Controlled UV irradiation induced the fastest aging, reaching a CI of 0.55 within 20 d; (3) Pond water-aged M-MPs (P-MPs) exhibited a Cd(II) adsorption capacity of 2.11 mg·g⁻¹ , representing a 10.55-fold increase over that of pristine M-MPs, while their 2,4-DMA adsorption capacity was much lower than that of UV-aged M-MPs (UV-MPs) (0.14 vs. 0.55 mg·g⁻¹); (4) The adsorption differences originated from carbonyl groups on UV-MPs enhancing 2,4-dimethylaniline(2,4-DMA) uptake via nucleophilic interactions, whereas biofilm on P-MPs increased hydrophilicity and promoted Cd(II) adsorption. These findings demonstrate that environmental factors critically regulate M-MPs aging and pollutant sorption, thus providing a scientific basis for the environmental risk assessment and management of discarded masks.