Study On Water Environment Carrying Capacity Of The Inner Margin Of The Radiation Sandbar In The South Yellow Sea

Inner part of radial sandbanks( IPRS )is one of the coastal region which is famous for the fastest rate of tidal flat silting up in jiangsu province. Tidal flat long sustained silting offers resource utilization of huge potential coastal space. For reasonable exploitation and utilization of ocean,promoting the steady development of the economy and reducing the impact on the quality of water environment at the same time, the paper takes the IPRS as the study area.The paper also evaluate the pollution situation and degree of eutrophication of water environment by using multivariate statistical methods. Based on similarity of pollution in each survey stance, the paper classified the study area. By establishing the 2-d tidal current model, the paper analyzed hydrodynamic characteristics of the IPRS. According to the ocean load of main pollutants, the paper calculate the water environmental carrying capacity.The paper also discussed regional water environment carrying capacity based on the present water quality and analyzed the regional water environment bearing capacity Combined with the human development and utilization activities which provide a reference for the later development, the control of the emissions and the choice of drain outlet. The paper also provide scientific basis for the sustainable development of regional social economy and water environment protection.In this paper ,the main research results and conclusions are as follows:(1) Using single factor evaluation method to evaluate the radial sandbanks water quality status of 2015, and find that the waters of inorganic nitrogen and active phosphate in water pollution is most serious, followed by chemical oxygen demand(COD) and petroleum contaminants. Eutrophication of the radial sandbanks waters is serious and the highest degree of area is located in the Xiyang waterway, and the sandbank of Jiangjiasha and Gaoni and Xiaoyangkou is second eutrophication level.Governments should pay attention to prevent and control the occurrence of red tide. The main inflow rivers surrounding IPRS is Beiling river and Bengcha river. On the basis of water quality evaluation results in estuaries, the main pollutants of inflow rivers are ammonia nitrogen, total phosphorus and COD.(2) It is found that the pollution characteristics of Xiyang waterway are obviously different from those of other regions according to the similarity of pollution in the stations of the radial sandbanks. The area is the most polluted area in the whole investigation area, and its seawater has high Inorganic nitrogen content, high chemical requirements, high activity of phosphate content and high oil content of pollutants.(3) By establishing the mathematical model of the radial sandbanks analyzed the hydrodynamic characteristics of the IPRS. It is found that the flow field in this area is characterized by reciprocating flow, and the flow velocity in the tidal channel is obviously larger than that on the sandbank. Through the analysis of water tracer and the calculation of tidal flux, it is found that the trend of the IPRS is generally weak in the north, and the south side of the water has a tendency to transport northward. The main tidal transport path are Huangsha waterway, Kushui waterway, Lansha waterway and Xiyang waterway.There are net transport during each tidal cycle, and the transport trend of the Xiyang waterway is obvious in the north. There is a significant tidal channel nature, which is the pool of pollutants in the area. The contaminants in the east and south regions have the tendency to migrate to the Xiyang waterway, and the reason why the water pollution of the Xiyang waterway is the most serious is explained.(4) Based on the background concentration of pollutants and the water exchange rate in the IPRS, the tank-type model was used to calculate the water pollution capacity of the IPRS. It was concluded that a big tidal cycle can accommodate COD amount of 375.75t,active phosphate 1.93t; a small tidal cycle can accommodate COD amount of 216.54t, active phosphate 1.11t; inorganic nitrogen has been seriously exceeded and need to strictly control the amount of land emissions.(5) The construction of the reclamation project in the IPRS has little effect on the water exchange, but has a great influence on the net flux of the main tidal cross section, resulting in the IPRS to the Xiyang waterway of the net input decreased by about 25%, the Huangsha waterway and Lansha waterway to the IPRS of the net input decreased by about 50%. At the same time, the construction of the project hinders the exchange of water on the north and south sides of the IPRS, which has affected the pollutant migration ability in the area and reduced the water carrying capacity of the IPRS.