Study On Vertical Distribution Model Of Dissolved Oxygen Concentration Under Ice In A Cold Area Lake

Dissolved Oxygen(DO)is the basis of various aquatic respiration and metabolism.The concentration of dissolved oxygen is also one of the main parameters to determine the quality of lake water.It is closely related to the survival and reproduction of aquaculture organisms and the self-purification of water bodies.In the ice-covered lakes,dissolved oxygen is not only an important ecological parameter,but also one of the important indicators is isolated from the atmosphere of water air-water exchange process.The dissolved oxygen kinetics in water is a complex process involving physical and biological interactions.Understanding the trend of dissolved oxygen concentration under ice can provide a good theoretical basis to make the function of the dissolved oxygen concentration analysis.The main content of this paper and the results obtained are summarized as follows:First,the vertical distribution profile of the dissolved oxygen concentration at different moments under the ice sheet is drawn based on the field observation data of the dissolved oxygen concentration under the ice sheet of Valkea-Kotinen Lake in Finland at the year of 2011.It is found that the dissolved oxygen concentration decreases gradually with the depth of the water layer in the pre-frozen by observing the vertical variation characteristics of dissolved oxygen concentration in a large number of profiles.This change rule of the dissolved oxygen concentration in the initial ice sheet is in accordance with the "S" curve,which is suitable for the Logistic model.Therefore,the Logistic model of vertical distribution of dissolved oxygen concentration is established.In order to identify the relevant parameters in the model,a type of iterative approximation algorithm is proposed to identify the optimal parameter values of Logistic model.Secondly,the field observations of dissolved oxygen concentrations at different stages are further analyzed.It is found that the peak concentration(inflection point)became lower and lower as the duration of ice cementation increased.According to the variation characteristics of dissolved oxygen concentration,a normal distribution numerical model of the spatial and temporal distribution of dissolved oxygen concentration under ice sheet is established for the whole ice period,and the three characteristic parameters in the model are identified by time t.The dissolved oxygen concentration calculated from the normal distribution numerical model is in good agreement with the measured value.The dissolved oxygen concentration surface and the contour are smoother.Therefore,the model can better describe the spatial and temporal variation characteristics of dissolved oxygen in the ice of Valkea-Kotinen Lake.Finally,the characteristics of dissolved oxygen concentration are analyzed statistically.