Microplastics and mesoplastics as emerging contaminants in Tehran landfill soils: The distribution and induced-ecological risk*

Environmental pollution with microplastics (MPs) and mesoplastics (MEPs) and their potential risks to human health and ecosystem quality have aroused the concern of communities. Therefore, the pioneering study was conducted on Tehran landfill soil contamination with MPs and MEPs. 56 shallow and deep soil samples were collected from different landfill areas in the wet and dry seasons. The physical and chemical characteristics of MPs and MEPs were measured using a stereomicroscope and FTIR-ATR spectroscopy, respectively. The results showed that the average MP abundance in shallow and deep soil was 863 +/- 681 and 225 +/- 138 particles/kg soil, and for MEPs, it was 29.8 +/- 6.4 and 18.1 +/- 8.3 particles/kgsoil. The low-density plastic particles were separated completely by flotation with H2O, NaCl, and ZnCl2 solutions, but PVC was only separated by 90%. Over 90% of MPs and MEPs were LDPE, PP, and PS polymers, explained by their widespread applications in single-use products and their consumption in Iran. Films, white and black, and 0.1-0.5 mm were the dominant shapes, colors, and sizes of MPs, respectively. The prevailing MEPs were film-shaped and in white and yellow colors, with a size of 0.5-1.0 cm. Canonical correlation analysis indicated that total organic matter and moisture were highly correlated with MP shapes. The calculated polymer hazard index values have a wide range at different sampling points, and this index yielded hazard levels III-IV and II-IV for MPs and MEPs, respectively, while according to the pollution load index category, the hazard level of MPs and MEPs was I-II and I. The potential ecological risk index from combined polymers has been estimated to be of minor to extreme danger for MPs and of minor risk for MEPs. Our findings provided baseline data on MPs contamination in Tehran landfill soil and its associated ecological risk, which aids policymakers in implementing risk-reduction measures.