Aging behavior and leaching characteristics of microfibers in landfill leachate: Important role of surface mesh structure

Mesh-structured films formed by the post-processing of microfibers improves their permeability and dexterity, such as disposable masks. However, the aging behavior and potential risks of mesh-structured microfibers (MS-MFs) in landfill leachate remain poorly understood. Herein, the aging behavior and mechanisms of MS-MFs and ordinary polypropylene-films (PP-films) microplastics, as well as their leaching concerning dissolved organic matter (DOM) in landfill leachate were investigated. Results revealed that MS-MFs underwent more significant physicochemical changes than PP-films during the aging process in landfill leachate, due to their rich porous habitats. An important factor in the photoaging of MS-MFs was related to reactive oxygen species produced by DOM, and this process was promoted by photoelectrons under UV irradiation. Compared with PP-films, MS-MFs released more DOM and nano-plastics fragments into landfill leachate, altering the composition and molecular weight of DOM. Aged MS-MFs-DOM generated new components, and humus-like substances produced by photochemistry showed the largest increase. Correlation analysis revealed that leached DOM was positively correlated with oxygen-containing groups accumulated in aged MS-MFs. Overall, MS-MFs will bring higher environmental risks and become a new long-term source of DOM contaminants in landfill leachate. This study provides new insights into the impact of novel microfibers on landfill leachate carbon dynamics. Mesh-structured microfibers (MS-MFs), mainly derived from disposable masks, were accumulated widespread in landfills and released into natural environment. Once MS-MFs were discarded in landfills, their properties and environmental effects will change. Herein, this work combined multi-dimensional evaluation methods to deeply understand the aging behavior and potential risks of MS-MFs different from ordinary microplastics films, and revealed the correlation between the aging behavior and mechanisms of MS-MFs and leached DOM in landfill leachate. This study provides new insights into the impact of MS-MFs on landfill leachate carbon dynamics and helps policymakers develop regulations to manage and dispose of novel microplastic pollutants.