Characteristics and Distribution of Microplastics in Shoreline Sediments of the Yangtze River, Main Tributaries and Lakes in China—From Upper Reaches to the Estuary

Abstract Microplastics (MPs) pervade the environment and increasingly threaten both natural ecosystems and human health. In this study, we investigated MP particle concentrations in sediment samples collected from 54 sites along the banks of the Yangtze River and its major tributaries and on lakeshores. The main polymer types found in the samples were polypropylene (PP), polystyrene (PS), and polyethylene (PE). MP particle abundance in the various types of locations was 35–51968 particles/kg dry weight (d.w.) on the banks of the main river, 52–1463 particles/kg (d.w.) on the banks of tributaries and 2574–23685 particles/kg (d.w.) on lakeshores. Correlation between MP abundance and mean annual runoff of each upstream tributary was significant, which suggests that increased runoff brings more microplastic waste to streambank sediments. The most common shape of MP particles in all upstream samples was flake and in downstream samples it was foam. Small microplastic particles (< 0.050 mm) were predominant at all sites in this study and the minimum particle size in samples from the Yangtze river banks was 0.065 mm. Average abundance of MP particles on the shores of the source lake was 9069 particles/kg around the inlet but only 866 particles/kg around the outlet; the difference was due to interception associated with sedimentation and precipitation in the lake. This study provides data and presents a theoretical basis for the analysis of the accumulation and distribution of MPs in sediment in the Yangtze River basin.