Numerical Simulation Research On The Movement Trajectory Of Maine Floating Debris In Jiulong River Estuary-Xiamen Bay

Marine floating debris mainly refers to all the man-made or processed persistent pollution substances in the coastal sea or open Marine environment through various ways.Due to the development of coastal cities and population activities,a large amount of solid waste will be transported into Xiamen Bay through surface runoff,making the sea area a disaster area of floating garbage pollution.Previous studies have shown that there will be garbage convergence zone in the sea area south of Gulangyu during the ebb tide.In this paper,field tracer experiments were carried out,and numerical simulation experiments were carried out according to Lagrange principle and RungeKutta method.The field tracer experiment results show that the transport trend of floating garbage is mainly affected by the surface current,and the effect of sea surface wind is not obvious in summer when the wind is low.The floating garbage thrown into the vicinity of Gulangyu,Haicang and Jiyu during the emergency period is the main source of the garbage convergence zone on the south coast of Xiamen Island.The calculated results of the model are in good agreement with the field tracer experiment results.The flow field results show that the Jiulong River diluted water moves to Xiamen Island along the latitude along with the ebb tide and meets the flood tide near the shore.The vertical section of the section shows that the water near the low tide is obviously stratified and salt wedge structure appears at the bottom.At the same time,the surface and bottom flow velocities are opposite,which is consistent with the circulation structure of the front,and the baroclinic effect caused by the longitudinal salinity gradient changes in the surface water converges,so the floating garbage aggregates.The experiment also found that there is convergence of garbage near Zhangzhou Port and Yu Zaiwei.This is because the fresh water of Jiulong River and the high salt sea outside the sea will meet to form a salinity front,which leads to the clockwise movement of the ebb current in this area.and the small area of aggregation partly due to the influence of topography.The location of floating garbage convergence zone is affected by tide,runoff and wind stress,and tidal action plays a major role.The results are as follows:(1)On neap tide day,the positions of the two convergence zones moved towards Huli Mountain and the estuary,respectively;(2)In the event of extreme weather such as floods,the convergence zone will move northward to the eastern coast of Xiamen Island;(3)Wind stress has little influence.Due to the action of southwest wind in summer,it is easier to find floating garbage gathering near Baishi of Xiamen Island.