Mass concentration, spatial distribution, and risk assessment of small microplastics (1–100 μm) and nanoplastics (<1 μm) in the surface water of Taihu Lake, China

Micro- and nanoplastics (MNPs) have drawn growing concerns because of their potential adverse effects on aquatic ecosystems. However, limited information is available regarding their concentration and distribution in the actual environment, particularly for nanoplastics (NPs). Herein, forty-eight sampling sites were established across the entire Taihu Lake to comprehensively investigate small MNP (<100 μm) pollution. By pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), six kinds of MNPs in Taihu Lake, namely polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), and polymethyl methacrylate (PMMA) were quantified. Total mass concentrations of the six MNPs in the collected surface water samples ranged from 381 to 1356 μg/L. Specifically, the concentrations of small microplastics (1-100 μm) ranged from 229 to 1182 μg/L, and those of nanoplastics (<1 μm) ranged from 88 to 305 μg/L. The mass concentrations of the six MNPs were as follows: 20.3-635.7 μg/L for PE, 46.6-281.4 μg/L for PP, 81.8-410.6 μg/L for PET, 62.8-445.8 μg/L for PVC, <LOQ - 6.2 μg/L for PS, and <LOQ - 1.6 μg/L for PMMA. Risk assessment revealed that MNPs at the lake bays and river inflow areas posed a higher integrated risk compared to those in the central lake in terms of the Pollution Load Index. The Polymer Risk Index and Potential Ecological Risk Index revealed a high to extremely high risk for MNPs in Taihu Lake. This study contributes to a deep understanding of the impacts of small MNP pollution in Taihu Lake and provides an important basis for policy-makers.