The Study On Wulansuhai Lake Water Quality Variation Characteristics In Freezing And Thawing Process

Wuliangsuhai Lake accepts the irrigation drainage and return, domestic sewage, as well as industrial wastewater of Bayannaoer irrigation area of Inner Mongolia. Wuliangsuhai Lake is an important wetland for the local economic development. Wuliangsuhai Lake is contaminated and has the potential to pollute the Yellow River.Hence, it is necessary to study the water environment of Wuliangsuhai Lake. Freezing and Thawing has influence on lake environment. Using one dimensional lakes freeze simulater designed by the research team, the water quality characteristics is evaluated using fuzzy neural network method and the impacts of the freezing and thawing on the concentration of pollutants and on the water quality properties were analyzed. The main findings are listed as below:In order to evaluate the eutrophication pollution, salinization and organic pollution, it doesn’t only analysis TN、TP、EC、COD’s spatial and temporal variation in water and ice medium, but also analysis TN、TP、EC、COD’s spatial and temporal variation in water of nearly a decade ice-free period, which proves that freezing and thawing has an effect on the migration of the pollutants indeed.The fuzzy neural network model is used with MATLAB programming, the F-, COD, TP,TN are selected as evaluation indexes. A new classification standard of water quality is developed:the values of the model less than 1.402 is Ⅰ,from 1.402 to 2.513 is Ⅱ,from 2.513 to 3.494 is Ⅲ,from 3.494 to 4.471 is IV,from 4.471 to 5.327 is V,more than 5.327 is inferiorl Ⅴ. Based on fuzzy neural network model, the water quality of non frozen period is simulated, the characteristics change of the water quality condition in the non frozen period is fluculated, and there is no obvious change trend. In the process of freezing and thawing, water quality under ice during freezing gradually becomes poor, and gradually improves in the ice melting process. Through the simulation of the new fuzzy neural network model, combining with the new standard of classification and analysing of water quality, the lower the freezing temperature, the less quantity of pollutants be expelled. The larger the concentration of pollutants in the lake water, the larger quantity of pollutants in the ice freezing process be expelled.According to the mechanism of contaminant migration, there are 3.38 X 105t TP and 1.28×106t TN migrate from water to ice in the Wuliangsuhai freezing process.The substantial results to improve the entire lake water environment can be achieved to treat water below ice.