Microplastic abundance, distribution, and composition in the surface water and sediments of the Yangtze River along Chongqing City, China

Purpose Microplastics are considered emerging pollutants and already currently present in measurable quantities in aquatic ecosystems. However, information on the current status of microplastic pollution in the upper Yangtze River, the most important water body in China, is insufficient. In the present study, the abundance and distribution of microplastics in the surface water and sediments were investigated to obtain the characteristics of microplastic pollution in Yangtze River along Chongqing City. Materials and methods Ten sampling sites along Yangtze River in the Chongqing urban area were selected to collect surface water and sediment samples. Abundance and morphological characteristics of microplastics were determined by counting using a digital stereo microscope. Micro-Fourier transform-infrared spectroscopy (mu-FTIR) analysis was used to identify polymer type of the microplastics. Results and discussion The abundance of microplastics ranged within 46.7-204 n L-1 and 100-583 n kg(-1) dw (dry weight) in the surface water and sediment samples, respectively. Fibers and films were dominant in most of samples, and the average proportion of fibers reached 74.3% in surface water. Whether in surface water or sediments, most of the microplastics were less than 0.7 mm in size, and the average proportion of microplastics with a size of less than 0.3 mm reached 62.6% in the sediment samples. Moreover, fibrous and small were the primary characteristics of the microplastics. Polypropylene, polyvinyl chloride, high-density polyethylene, polyester, and wool fibers were identified in the surface water samples. Conclusion The Yangtze River along Chongqing City is contaminated by microplastic, like many urban rivers. Anthropogenic activities, including sewage treatment effluents, might be the main sources of microplastic pollution in Yangtze River (Chongqing urban section). This study reveals the contamination and characteristics of microplastics in the Yangtze River along Chongqing and supplies important data for further research on microplastics in Yangtze River's basin.