Distribution characteristics and pollution risk assessment of microplastics in urban rivers: A case study in Yitong River, China

Rivers are crucial channels for microplastic (MP) transport from land to water environments, underscoring the importance of studying the distribution characteristics and pollution risk levels of MPs in river water and sediment. In this study, the abundance, shape, size, color, and polymer type of MPs in water and sediment in the Yitong River were determined. The results showed that MP abundance was higher in the rainy season than in the dry period, with urban sections generally exhibiting higher MP abundance than rural areas. The MPs were predominantly fibrous, ranging from 0.05 to 1 mm in size, and primarily black and transparent in color. Eleven polymer types were identified, with polyethylene (37.27 %), polypropylene (29.09 %), and polystyrene (12.73 %) being the top three. Scanning electron microscopy (SEM) revealed that the surface of MPs was rough, with varying degrees of holes and cracks, facilitating the attachment of other pollutants. The assessment of MP pollution based on the pollution load index (PLI) method indicated slight MP pollution, with a PLI value of <10 for the water body and <1 for the sediment. The assessment of the distribution characteristics and pollution levels of MPs establishes a foundation for the comprehensive analysis of MP pollution. It offers valuable guidance for managing MP pollution in the Yitong River and provides basic data for assessing the distribution characteristics and pollution risks in mid-temperate urban rivers.