Influence of landfill leachate microenvironment on the occurrence of microplastics: TOC changes are the main driving factor

Factors such as inorganic salts, heavy metals and organics in landfill leachate can affect the environmental behavior and transport properties of microplastics. However, the influence of the microenvironment on the behavioral effects of microplastics in landfill leachate is still limited. In this study, the abundance characteristics of microplastics in leachate from 15 landfills in the North China Plain were investigated. The results showed that the abundance of microplastics in the leachate in this region was 712.0 items/L, which was mainly composed of small particle size and long fibrous microplastics. The relationships between leachate physicochemical factors and microplastic accumulation patterns were explored using models such as structural equations. Among them, TOC (Total Organic Carbon) had the strongest driving effect on 50-100 μm microplastics. And it had different effects on different microplastics: it promoted the degradation of PET (Polyethylene terephthalate), while it inhibited the degradation of PVC (Polyvinyl chloride), FVMQ (Fluorosilicone rubber) and PSU (Polysulfone). The ridge regression model indicated that the interaction of landfill age with Cr (Chromium) and the interaction of redox potential with Cr were the key factors influencing the behavioral characteristics of microplastics in leachate. These results provide a scientific basis for the treating waste leachate and the controlling the emerging pollutants.