Classification and identification of polar pollutants on microplastics from freshwater using nontarget screening strategy

Microplastics (MPs) cause an increased threat to the freshwater environment by adsorbing pollutants on their large surface area. Considering their adsorption characteristics, non-polar pollutants with high distribution coefficients have been studied extensively. However, comprehensive research on the types of polar pollutants adsorbed by MPs is lacking. In this study, a nontarget screening strategy, including classification and identification, was performed to analyze the pollutants adsorbed by MPs in Tai Lake and the Yangtze River. Compared with the pollutants adsorbed or added to raw plastics, more types of polar pollutants were found on MPs from freshwater. The nontarget classification of 4723 features on MPs from freshwater and 680 features from raw plastics were annotated based on the mass spectrometry spectra. Further identification with multiple platforms identified hundreds of pollutants absorbed by MPs in Tai Lake and Yangtze River, including industrial intermediates, medicines, and surfactants, exceeding those adsorbed by raw plastics, showing an enrichment of the pollutants on MPs in freshwater by secondary adsorption. Our study is the first to use nontarget analysis to comprehensively demonstrate MP adsorption and release of pollutants in freshwater environment, providing a significant reference for the research of MPs and the management of the water environment.