[Temporal and Spatial Distribution and Risk Assessment of Microplastics in Multiple Media of an Urban River]

The increasingly serious pollution of microplastics （MPs） in urban rivers has attracted global attention. At present, there is a lack of research on the spatiotemporal distribution of microplastics in inland rivers. In order to understand the spatiotemporal dynamic characteristics of microplastics in urban rivers, water and sediment samples were collected from the Guanzhong section of the Weihe River Basin during the wet and dry seasons. The abundance, morphological characteristics, and polymer types of microplastics in the sediment were systematically studied using multiple density flotation extraction and spectral analysis methods to clarify the spatiotemporal distribution and migration characteristics of microplastics in the watershed. The results showed that the variation range of microplastics in river water was 1.02-10.32 items·L^-1, and the variation range of microplastics in sediment was 220.30-2 840.40 items·kg^-1. Both surface water and sediment showed significantly higher abundance during the dry season than during the wet season （P<0.05）. The particle size of microplastics was mainly small particles with sizes of <0.1 mm and 0.5-1 mm, and fibers were the main shape of microplastics in the sediments. Polyethylene （PE） and polypropylene （PP） were the main types of microplastics. The overall pollution risk was mild pollution. The results of this study can provide some reference for the scientific understanding of microplastic pollution in urban rivers and the formulation of plastic control measures.