Simulation On The Transport Characteristics Of Pollutants In Daling River Estuary

Daling Estuary is located in the northern sea area of Liaodong Bay,adjacent to the Liaohe Estuary,and is an important part of Liaoning coastal economic belt.Over a long period of time,daling river basin social economy high speed development,daling river coast city of life and production activities to produce a large amount of sewage discharged into daling river,into the estuary area,result in higher levels of daling river mouth area pollutant concentration,large area of sea water quality standard Ⅳ class or bad Ⅳ class rank,severe pollution.In recent years,China has attached great importance to the protection of the Marine environment and carried out a number of remediation actions to control the pollution in the Liaodong Bay,and the Daling Estuary has attracted much attention.Therefore,this paper,by establishing a numerical model and comprehensively considering the combined action of river runoff and tide,analyzes the transport characteristics of pollutants in the Daling Estuary,and provides a scientific basis for the development and management of the Daling Estuary and environmental protection.In this paper,the hydrodynamic numerical model is used to simulate the tidal current in the Liaodong Bay,and the validity of the model is verified by comparing with the measured tidal level and tidal current data.The tidal current simulation results show that the tidal current in the Daling Estuary area is irregular semi-diurnal,and the flow velocity of rising and ebb is between 0.20 m/s and 0.60 m/s,and the residual current intensity is weak.Based on a well-validated hydrodynamic model,a pollutant transport and diffusion model was used to simulate the concentrations of inorganic nitrogen(DIN)in the sea-based river in the Daling Estuary under three flows of abundant,flat and dry seasons,respectively.In addition,the distribution of DIN concentration in Daling Estuary under SSW gale in summer and NNW gale in winter was simulated by the statistics of gale weather in this area.The results show that the concentration of DIN in Daling Estuary is greater than 0.4 mg/ L at the flow rate in wet season and normal season,and the pollution is serious.Under the flow rate in dry season,the concentration of DIN in Daling Estuary decreases greatly,and the water quality is improved obviously.The addition of wind field can effectively enhance the water exchange capacity in the Liaodong Bay,but the SSW wind does not significantly reduce the DIN concentration in the Daling Estuary,while the NNW wind reduces the DIN concentration in the Daling Estuary by about 60%,which effectively improves the water quality in the area.Furthermore,through the establishment of particle tracking model,Lagrange neutral particles were used to simulate the transport characteristics of pollutants in the Daling Estuary under the above working conditions.Results show that because of the daling river mouth there are a large areas of intertidal shoal nearshore,form the intertidal zone,mainly through the shallow water on the tidal creek,weak hydrodynamic and water exchange,poor ability of contaminant particles flow daling river,under the impetus of the trend,most of the stranded in shallow water on either side of the daling river estuary,a few spread to the coast.Reducing the runoff of Daling River reduces the amount of pollutant particles flowing into Liaodong Bay,and the number of pollutant particles near the Daling River estuary decreases obviously.In addition,the simulation results under the wind field conditions show that the prevailing NNW strong wind in winter can effectively improve the transport and diffusion capacity of pollutants in the Daling Estuary,and greatly improve the water quality of the Daling Estuary.