Occurrence Characteristics and Ecological Risk Assessment of Microplastics in the Water Body of Lake Gahai, Tibetan Plateau of China

Microplastics (MPs) pollution has emerged as a significant global concern. Research on the sources, distribution, and ecological risks of MPs in the lakes of the Tibetan Plateau remains relatively scarce, thereby hindering efforts to clarify the current status and transport patterns of MPs in these aquatic systems. This study examines the surface water of Lake Gahai—a representative permanent freshwater lake located on the northeastern margin of the Tibetan Plateau—to analyze the abundance, size distribution, and polymer types of microplastics. By integrating existing literature, we discuss the primary transport pathways of MPs in the study area and quantitatively assess ecological risks using the pollution risk index (H), pollution load index (PLI), and potential ecological risk index (PRI). Results indicate that the abundance of microplastics (MPs) in the surface water of Lake Gahai varied from 3.33 to 82.00 items/L, with an average abundance of 30.07 ± 24.70 items/L. The majority of MPs were found within the size range of 20–50µm, constituting over 64.42% of the total. A total of 35 polymer types were identified, predominantly including polyethylene (PE), polyethylene terephthalate (PET), polyamide (PA), polylactic acid (PLA), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polypropylene (PP), acrylate polymers, and polyvinyl alcohol. The ecological risk assessment revealed that the pollution load index (PLI) of the lake's surface water was low, while both the hazard quotient (H) and the pollution risk index (PRI) reached the highest severity level. These findings enhance the understanding of the sources and ecological risks associated with MPs in the aquatic environment of the Tibetan Plateau and provide valuable data and theoretical support for future research on MPs pollution.