Numerical Modeling Studies On The Effects Of The Liao River Discharge On The Transport And Dispersion Of The Pollutants In Liaodong Bay

With the rapid development of coastal cities and the marine economy in recent years,large amounts of pollutants have been released into the sea,exacerbating the marine environment gradually.As a hotspot of China's economy,Liaodong Bay receives large amounts of pollutants coming from land sources every year.River input is a main form of land sources,making the river discharge being one of the important factors that affects the flux and the dispersion of the pollutants.Therefore,investigating the influence of the Liao River discharge to the transport and dispersion of pollutants in Liaodong Bay can provide relative theoretical basis and realistic reference for the management of the marine environment.In this article,MIKE was used to build the three dimensional flow numerical model,then the river discharge,heat flux and other factors were considered in the calculation,and the model was verified using the measurements of tide,tidal current,temperature and salinity.The results show that the constructed model is able to well reflect the characteristics of the hydrodynamics,temperature and salinity of the large scale model and provide accurate dynamic field for the small scale model of Liaodong Bay.The three-dimensional water quality model of the small scale model was built after the large scale model was accurately verified,and then this model was validated using the measurements of annual-averaged concentration of the surface inorganic nitrogen and active phosphorus.The concentration distribution of the surface inorganic nitrogen and active phosphorus in Liaodong Bay in 2009 was then simulated,and the influence of the variation of the Liao River discharge to the concentration distribution and the impact of the decrease of the flux of the pollutant input from the Liao River on the water quality of Liaodong Bay were also discussed.The results demonstrate that the concentration of the surface inorganic nitrogen and active phosphorus in Liaodong Bay is relatively high in autumn and winter and will gradually decrease in spring and summer.The concentration of the surface inorganic nitrogen presents such distribution characteristics that it gradually decreases from the northeast to the southwest,from the east to the west and the high concentration appears around the Liao River estuary and the Daliao River estuary.The concentration of the surface active phosphorus of east bay is higher than that of west bay in the whole year and it gradually decreases from the northeast to the southwest in spring and summer.During the flood year(the drought year),with the concentration of the inorganic nitrogen and phosphorus input from the Liao River remaining the same,the increase(decrease)of the Liao River discharge won't change the temporal distribution characteristics of the surface inorganic nitrogen and active phosphorus,but the concentration of them in the whole Liaodong Bay will change correspondingly and the variation near the Liao River estuary is more significant.Thus,in this case increasing(decreasing)the Liao River discharge,the water quality in Liaodong Bay will be worsen(improved)to some extent.The water quality of Liaodong Bay will be improved when the flux of the pollutants input from the Liao River decreases with the Liao River discharge remaining the same.The trajectory of the conservative pollutant particles was simulated with the concentration of the particles input from the outlet remaining the same.The simulated results show that the majority of the particles will accumulate around the estuary and the amount of the particles in the northeast is larger than that in the southwest.As the discharge increases(decreases),the total amount of pollutant particles will increase(decrease)and the number of particles near the Liao River estuary will change more obviously.