[Occurrence, Driving Factors, and Risk Assessment of Microplastics in Surface Water of Typical River Basins in the Yangtze River Delta, China].

Rivers and lakes are important channels for the migration, transformation, and transportation of microplastics （MPs） pollution from land sources into the sea. A large number of studies have investigated the pollution characteristics of MPs in different watersheds, but little to none have considered the driving factors for spatial distribution based on network analysis. In this study, Taihu Lake, Taipu River, and Huangpu River in the Yangtze River Delta were selected as the target area. Microplastics were analyzed based on field sampling, stereomicroscopy, and Fourier transform infrared spectroscopy. According to the results, MPs were 100% detected at all sampling sites. The abundance of MPs in the surface water of Taihu Lake [（7 076±1 886） n·m-3] was significantly higher than that of the Taipu River [（4 400±2 839） n·m-3] and the Huangpu River [（2 800±1 315） n·m-3], indicating a significant spatial distribution difference. The particle size of MPs was mainly distributed in the range of 0.1-0.5 mm, with transparent, black color, and fibers as the main MPs. Polyethylene terephthalate （PET）, polystyrene （PS）, and polyamide （PA） were the major contributors of polymers, accounting for 59.5%, 10.4%, and 8.67%, respectively. Correlation analysis showed that the MPs abundance was significantly positively correlated with total nitrogen （TN）, Co （R=0.436,P<0.05）, and Cd （R=0.478,P<0.05）, whereas they were negatively correlated with Cu （R=-0.456,P<0.05）. The MPs abundance was also significantly negatively correlated with the distance from sampling points to the factory area （R=-0.796, P<0.001）. Industrial point source emissions played an important role in the migration and occurrence of MPs. The co-occurrence patterns of MPs, metal elements, and water quality index were explored based on network analysis. TN and PS were the core influencing factors. Compared with other studies in the Yangtze River Delta, the risk pollution load index of surface water MPs in the watershed was 1<PLIZONE<2, which was characterized as light pollution. The overall ecological risk of MPs in the surface water of the research basin was relatively low.