Occurrence of microplastics in landfill systems and their fate with landfill age

Microplastics (MPs) are emerging pollutants that have been extensively detected in marine and terrestrial environments. Landfills are receptacles for cumulative loading of plastic waste derived from industry and households, but data on MPs occurrences in landfill systems are lacking. In the current study, the occurrence, characteristics and distribution patterns of MPs in landfills (including leachate and refuse) of the megacity Shanghai were investigated in accordance with different landfill ages (3-20 years). The results revealed that the average abundances of MPs in leachate and refuse were 8 (±3) items/L and 62 (±23) items/g, respectively. The predominant shapes and polymer types of the detected MPs were fibers and cellophane in leachate, whereas they were fragments and polyethylene in refuse. The patterns of abundance and size distribution of MPs in refuse varied from different landfill age, and different polymer MPs exhibited various occurrence patterns with increasing landfill age. Further spectra analysis suggested the presence of oxidative degradation of polyethylene MPs in the landfill process, especially for the landfill time of more than 20 years, so the fates of MPs in landfills were determined by the increase consumptions of plastics products and the degradation process of MPs in landfills. This study firstly provided a systematic overview of MPs pollution characteristics in landfill systems, and the results will foster the understanding of MPs fates over a long time scale in the environments.