Water Exchange And Pollution Diffusion Between Yangtze Estuary And Hangzhou Bay

There are complex physical processes in the estuary coastal waters where the inland runoff and the offshore tides meet,and those processes could significantly affect the flow field characteristics.The estuary of the Yangtze river,which is the largest river in China,is adjacent to hangzhou bay where the tides are strongest.It is important to study the confluence of water and pollutants diffusion in hangzhou bay of Yangtze estuary.In this paper,a large-scale two-dimensional tidal mathematical model is established for the water exchange of Yangtze estuary and Yangtze bay.Numerical simulation of the flow characteristics of the Yangtze estuary and Yangtze bay and its intersection area.Finally,the trajectory of the tracer particle is obtained and the results show that Yangtze estuary water mostly flows into the sea,and the remainder bypass Nanhui port and go straight to Yangtze bay and arrived in Jinshan.The north shore water of Yangtze bay can spread to the downstream of Jinshan mountain of 35km,and the south bank water can spread eastward as far as Zhoushan sea area.According to tracer particle trajectory analysis,the water flow convergence zone between Yangtze estuary and Yangtze bay estuary extends from Jinshan to the east about 35km,and from the north bank to the south about 40km.The influence of runoff on water dynamics at Yangtze estuary and junction is analyzed,and the increase of runoff increases the ebb and flow velocity of water flow in the southern branch and the junction area,while the increase of runoff has little effect on the north branch flow.This paper treat conserved substance as pollution factor,and building a model consistent with the trend of water quality,a wide range of Yangtze bay sea dilution diffusion of pollutants in the Yangtze river estuary is simulated and the mutual influence of two estuaries water quality,this paper studies the interchange conservative substance concentration of time change.Numerical tests show that point source pollutants discharged from the Yangtze estuary migrate to and fro with the tide and eventually diffuse into the sea,partially diffusing into the northern coastal waters of Yangtze bay,with the concentration reduced to 5‰.The point source pollutant discharged from the north bank of Yangtze bay diffuses from north to south as it diffuses up and down.The northern bank of Yangtze estuary and Yangtze bay discharged pollutants of the same concentration,and the concentration diffused to the vicinity of nanhui estuary decreased to 0.9%and 1‰,respectively.The concentration at the junction was affected by Yangtze estuary and Yangtze bay by about 9:1.Simulation analysis of the Yangtze estuary and Yangtze bay when the discharge of pollutants concentration changes,abundant,water pollutants concentration contour is given by area,surrounded by low concentration area during altogether more than in dry season,the high concentration zone just on the contrary,shows that the runoff pollutants spread fast and high degree of dilution.