Distribution, characteristics, and research status of microplastics in the trunk stream and main lakes of the Yangtze River: A review

Microplastic pollution has become an environmental issue of great concern owing to the persistence of microplastics and their potential adverse effects on biota. The Yangtze River is the longest river in China and the third-longest river in the world, and the microplastics in this river will affect the health of a large population living along with it. To ensure the survival safety of people, it is essential to plan ahead and investigate in advance in order to understand the microplastic pollution in the river and work out countermeasures. This paper reviews the literature concerning the microplastic pollution in the Yangtze River basin and analyzes the abundance, shapes, colors, and composition of microplastics in the water bodies and sediments in the trunk stream and main lakes of the Yangtze River. The results are as follows. Compared to other river basins in China and abroad, the microplastics in the Yangtze River basin have a moderate abundance and high spatial heterogeneity. Owing to the barrier effect of the Three Gorges Dam on microplastics, the abundance of microplastics in the Three Gorges Reservoir is generally an order of magnitude higher than that in other sections of the river. Most microplastics in the water bodies and sediments are less than 1 mm in size and are transparent and colorful. In terms of shapes, they are dominated by fibers, followed by fragments and films. In terms of composition, the microplastics in the source region of the Yangtze River are mainly composed of nylon and polyethylene, while the microplastics in the surface water from the lower reaches of the Jinsha River to the Yangtze River estuary are dominated by polypropylene and polyethylene. The microplastics are primarily derived from the secondary microplastics in the environment, and relatively intensive human activities increase the abundance of microplastics. These results serve as bases for understanding and preventing microplastic pollution in the Yangtze River.