Study On Mathematical Modeling Of Eutrophication Of Great Water Body

Eutrophication is one of comprehensive environmental problems existing in the world. As the engineers and scientists increase understanding of mechanism of eutrophication and technology of computer is improved, more and more eutrophication studies focus on the mathematic modeling of eutrophication. Some problems related to the mechanism and mathematical modeling of eutrophication were studied systemically in this paper. The first part of the thesis introduced the current advances on the eutrophication in aspects of mechanism, mathematical modeling and control of eutrophication. According to global phosphorus and nitrogen circulation, excess nutrient discharged into freshwater is the main reason of eutrophication. This paper discussed the main biological, chemical and physical changes of plankton, nitrogen and phosphorus in the process of eutrophication and a new assess standard of eutrophication was put forward. On the base of these work, the theory and technique which deal with ecological modeling ,two-dimension ecological dynamic model and stochastic eutrophication model was researched thoroughly. The mostly innovations of the dissertation included:The two-dimension ecological dynamic model was founded, which could simulate the eutrophication of water body with complex boundary. The eutrophication models of lakes at present used right angle coordinate system and were suitable for the water body with simple boundary. In order to resolve this problem, the boundary-fitted curvilinear coordinate system was utilized and inerratic reservoir region was changed into rectangle rigon.Recently, the theory of stochastic differential equation was applied to the water quality models of river. However, there was little stochastic eutrophication model in literature. Based on the Vollenweider model, a stochastic eutrophication model was built. The changing process of total phosphorus concentration was regarded as a random process in the model. If the random properties of initial conditions were obtained, the analytical solution as well as the numerical solution could be found. Therefore, the model provides the random properties of total phosphorus concentration, such as the mean and variance.In addition, the model of nonpoint pollution in wet area was researched as wellas the assess standard of eutrophication. Some laboratory studies were conduced to remove nutrient from water bodies and some useful conclusions were obtained.