Composition and Distribution Characteristics of Microplastics in Danjiangkou Reservoir and Its Tributaries

Microplastic pollution is a hot topic in environmental science. To explore the microplastics in Danjiangkou Reservoir, a national first-class water source protection area, we studied their types, abundance, and material characteristics using density flotation and micro-Raman spectroscopy. The spatial distribution characteristics of microplastics were also revealed according to the hydrologic and hydrodynamic conditions of the reservoir. The results showed that the main types of microplastics were fragments (84.2% of the total), granules, films, and fibers, of which 84.2% were fragments. The numbers of each type of microplastic were significantly different in different areas. A variety of colors were observed, with transparent and brown microplastic being most common. During the wet season, the average abundance of microplastics in the reservoir was 7248 n·m-3, which is higher than that observed in the Han Reservoir. The particle sizes of the microplastics in the research area ranged 75-4703 μm, of which 73.4% had a particle size of less than 500 μm; microplastic abundance was inversely related to particle size. Nylon was the most common form of microplastic in Danjiangkou Reservoir, accounting for 36.4% of the total, followed by polyethylene (PE) and polypropylene (PP).