Distribution and characteristics of microplastics in the Yulin River, China: Role of environmental and spatial factors

As inland freshwaters act as a major transport pathway for marine microplastic pollution, microplastic pollution in freshwater systems has recently received growing attention. However, the role of environmental and spatial factors in shaping the distribution and characteristics of microplastic pollution in reservoir ecosystems is not well understood. Here, we studied microplastic pollution in the surface water of the Yulin River, a typical tributary of the upper reaches of the Three Gorges Reservoir (TGR). The abundance of microplastics were 1.30 × 10, 1.95 × 10 and 3.60 × 10 items/L in the mainstream, tributaries and bays of the Yulin River, respectively. Polyethylene, polypropylene, and polystyrene were identified as the predominant types. The most common shapes were line/fiber and foam. Small-sized particles dominated the collected microplastics. Aged surface was identified by scanning electron microscopy and X-ray photoelectron spectroscopy. The microplastics in the Yulin River were largely of secondary origin. Microplastic pollution varied in space. The abundance of microplastic was higher upstream reaches than downstream, which was correlated with anthropogenic activity. The backwater of the TGR increased the abundance of microplastic in the estuary of the Yulin River. The abundance of microplastic was negatively correlated with the channel width. This study is helpful for understanding the characterics and distribution of microplastics in reservoir ecosystems within underdeveloped area, and can thereby inform well-directed strategies to mitigate microplastic pollution.