Tributary inflows enhance the microplastic load in the estuary: A case from the Qiantang River

Microplastics (MPs) in the surface water of the Qiantang River and its tributaries were investigated in this study, to evaluate the contribution of riverine discharge on emerging pollution load in the Hangzhou Bay. The abundance of MPs (mean 1183 ± 269 particles/m³) showed spatially and temporally heterogeneous in the surface water. Polyamide, polyester, and polyethylene teraphalate were the major components, accounting for 77.4% of all polymer types. Fiber was the most common shape, indicating the potential anthropogenic sources of MPs. The MPs flux from the Qiantang River to the Hangzhou Bay was estimated to be 2831 tons/year, implying the importance of riverine discharge in an estuarine bay. The inputs from the complicated tributaries system led to a 20-fold increase of MPs flux, and would significantly improve their budget of downstream and estuary, so we suggested the control and management on plastic pollution should be strengthened in all aspects.