Study On The Distribution Characteristics Of Microplastics In Zhoushan Lincheng River And The Migration Law After Entering The Sea

As an emerging type of pollutant,microplastics have been shown to have a significant impact on ecology when their concentrations are too high.The distribution of microplastics in the environment is not uniform,making it necessary to investigate the spatiotemporal variation of microplastic abundance and its influencing factors.Surrounded by the sea on all sides,Zhoushan Island has faced a great threat to its coastal environment due to the rapid pace of urbanization in recent years.Large quantities of microplastics are being discharged into nearby waters,migrating under the influence of ocean dynamics and potentially affecting the surrounding fisheries.As such,studying the migration model of microplastics in the waters near the Zhoushan Archipelago can provide a theoretical foundation and aid in marine pollution control efforts in the area.Lincheng River is an ocean-flowing river in Zhoushan island,and the microplastic distribution and its influence factors were analyzed in this studied.During the wet season(July 2021),the dry season(November 2021)and the typhoon season(September 2021),microplastics in the river water and sediments were detected.The results pointed out that microplastics was distributed in all reaches of Lincheng River and the abundances were at a medium level in comparison with other rivers.In the surface water,blue man-made Cellulose(CE)was the main microplastics,but in the sediment,the most detected microplastics were Polypropylene(PP)and Polypropylene Polyethylene Blends(PP+PE)with the form of fragments and the color of blue and green.The abundance of microplastics in river water in the wet season is higher than that in the dry season,typhoons and local construction activities may increase the microplastics abundance.Besides,watershed construction index(B)was proposed in this study and a high positive correlation with the abundance of microplastics was founded,which illustrated the development of coastal cities highly contributed to the microplastics pollution.A two-dimensional hydrodynamic model was developed using Mike 21 software to investigate the migration of microplastics in the waters surrounding the Zhoushan Archipelago and the East China Sea.The model considered various factors such as tides,ocean currents,and wind fields,while ensuring the accurate verification of tidal levels,flow velocities,and flow directions.The particle tracking module was utilized to release microplastics at the mouth of the Lincheng River and observe their spatial distribution and migration paths.Tuanjishan Island,where waste generated in Zhoushan accumulates,has become a potential source of microplastic pollution,so the research focused on predicting the migration patterns of microplastics released from this island and their potential impact on Zhoushan’s fisheries.The study showed that the distribution of floating microplastics varies significantly with the seasons due to the effects of seasonal ocean currents and monsoons.During summer,microplastics spread northeastward,while during winter,they move southwestward.Microplastics released at different locations during different seasons accumulate near the release points and in the deep waterway between Zhoushan Island and Ningbo.The distribution of microplastics released from Zhoushan Island is closely related to the ocean front,which prevents microplastics from spreading outward.