Numerical Simulation Of The Distribution Of COD And Its Influlunce Factors In The Bohai Sea

The Bohai Sea is a typical enclosed area surrounded by the Chinese mainland and Liaodong Peninsula and connected to the Yellow Sea with its narrow Bohai Strait. In the recent years, red tides often occurred and the extent of red tide appearance had a tendency to spread widely. The aggregation of the pollution of the Bohai Sea has influenced the economic of the cities around the area and been threatening the lives of the people in these cities. Under the present situation, it is necessary to control the pollution of the Bohai Sea.Analyzing the polluting conditions, the eutrophic index and the water environmental carrying capacity by water quality models in the research of the water quality and the environmental reconditioning has the advantages of shorter time, less cost and more predictabilities.The mathematical model applied in this paper includes a 3D hydrodynamic model and a 3D water quality model. The basic hydrodynamic equations are based on the conservation of mass, momentum and scalar transport under Bossinesq assumption. TVD numerical scheme based on Finite Volume conception and space staggered grid system is adopted, using 4km x 4km mesh in the horizontal plane and 17 layers in the vertical direction. The typical seasonal (summer and winter) residual circulation in the Bohai Sea is studied with the 3D hydrodynamic model on the basis of accuracy validating. The precesion is rather good. In this paper, the data of initial distributions and loads of pollutions are analyzed and dealed with space interpolating. The distributions of COD in the Bohai Sea and the concentrations in the regions of the Bohai Sea are simulated, and the result is good compared with the observed data .Then this paper analyzed the driving factors on the distributions of COD in the regions of the Bohai Sea and drew the conclusions: The pollution of the Bohai Sea is mainly induced by the loads from the land. In the Liaodong Bay and the Bohai Bay, the dispersion and the decomposability of the pollutions are the main ways of water purification, but in the Laizhou Bay and middle Bohai Sea, the water change are of more importance. The load of the Dalian Bay in the Huanghai Sea doesn't cause much pollution to the Bohai Sea.