Occurrence and distribution of microplastics in China's largest freshwater lake system

Although microplastics (MPs; < 5 mm) have been recognized as one of the most challenging environmental pollutants in the ocean, our understanding of the environmental fate of freshwater MPs falls far behind, particularly on smaller MPs (<0.1 mm). Here, we seek to reveal the latest MP pollution status in the largest freshwater lake of China, Poyang Lake, by comprehensively assessing the abundance, distribution, size, shape, polymer composition, and micro-morphology of MPs in water and sediment, covering a large geographic area of the Lake and its five main river tributaries. High levels of MPs were detected in water (up to 1064 ± 90 MP/m³) and sediment (up to 1936 ± 121 MP/kg), with the highest concentrations in the Gan River and the lowest in the national Nature Reserves. While a positive correlation was identified between MP abundance in water and sediment, the size distribution of MPs in between water and sediment was distinct. The dominant MP form in sediment and water was fragment and fiber, respectively. Infrared spectroscopy analysis confirmed the dominant polymer types including polypropylene, polyvinyl chloride, polyethylene, polystyrene, and polyvinyl alcohol. Moreover, both μ-FTIR and SEM results suggested significant features of weathering and fragmentation of MPs. This study provides comprehensive data to understand the environmental behavior and pollution magnitude of MPs in China's largest freshwater lake and highlights the significant contribution of smaller-size fractions (0.03-0.1 mm) to improve future MP studies in freshwater systems.