Distribution characteristics, source analysis, and ecological risk assessment of microplastics in Ulungur Lake, China

While significant advances have been made in global microplastic (MPs) pollution research in recent years, more fundamental research is still required for semi-closed or closed water bodies, such as lakes. This study presents the first systematic assessment of the contamination characteristics, sources, and preliminary ecological risks of MPs in Ulungur Lake - the largest freshwater fishery base in northern Xinjiang. Results demonstrate MPs abundances of 0.32-8.82 n/L (surface water) and 18.2-223.6 n/kg (sediments), with spatiotemporal heterogeneity. Micro-Raman analysis revealed polyethylene terephthalate (PET) and polyethylene (PE) dominated polymer composition, while white (54.17 %) and black (32.32 %) fibrous MPs (0.1-0.5 mm) were most prevalent. Source apportionment, integrating Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA), along with weighted allocation models, identified agricultural activities (28.6 ± 3.2 %) and anthropogenic inputs (22.1 ± 2.8 %) as the primary contributors. The Potential Ecological Risk Index (PERI) quantifies composite ecological hazards, classifying the lake as high-risk overall, with extreme-risk levels (PERI = 1541.46) in the rural farmland area (W6), necessitating prioritized monitoring and tailored mitigation strategies. As the first systematic, multi-scale ecological risk assessment of MPs pollution in northern Xinjiang's arid inland region, this study provides critical insights for ecological conservation and sustainable management of Ulungur Lake.