Research And Application Of Algal Blooms Risk Evaluation Method Based On Algal Accumulation Dynamics Model

In recent years, rapid economic development has caused a sharp increase in the quantity of pollution discharged, making pollution control an increasingly relevant issue to our society. The frequently water blooms in eutrophic surface water has restricted the function of water delivery, destroyed the aquatic ecosystem balance, degraded water quality, and directly threaten the security of drinking water under the influence of continuous increase of water pollution load. The problem of algal bloom risk has become one of the key environmental problems in rivers, lakes and reservoirs of China, which should be solved desideratly at present and in the future.The evaluation and prediction of algal bloom risk for eutrophic water is an important means of water environmental management, it is also the significant gist to carry out emergency management. Therefore, in order to forecast the entrophication trend faster and more scientifically, the research of algal bloom risk evalution model should be strengthened. The evalution model can provide the powerful technological support for the emertency management of the water environment management department, and it is essentially important for lessening the impacts of water bloom and ensuring the sustainable development of social economy.In this paper, based on the comprehensive study of water environmental evalution mathods at home and abroad, a algal blooms risk fast assessment methods and a algal blooms risk assessment model based on detailed information are established through deeply analyse the dynamic model of algal accumulation. The main research contents of the paper are as follows:(1) Considering the influence of multi-factor on ecological receptor, a multi-factor risk assessment method based on biological accumulation dynamics model was developed, the model can simulate the real-time change of environmental risk under the common cumulative impact of environmental factors.(2) Based on the research of the effect of the pollution process on changes of water quality, the algal bloom risk assessment model is developed, the model concludes watershed non-point source submodel, water quantity and quality submodel, and eutrophication of ecological dynamic submodel.(3) The algal accumulation dynamics model is developed by the analysis of algal concentration accumulation process based on biological accumulation model. (4) Based on multi-facor risk evalution theory and algal accumulation dynamics model, considering the factors such as meteorology, hydrology, water quality and biological continued influence on algal risk, a new algal risk assessment model with a simple model structure and fast calculation process is built according to the current water quality condition of our country. The assessment method can realize the fast simulation and forecast of the levels of algal bloom risk and the outbreak time of water bloom, and provides technical support for water quality management.(5) Non-point resource pollution models are developed for the watershed scale. Area division and information extraction is carried out based on the GIS platform. The model improves the eutrophication ecosystem dynamic model.(6) The release experiment of sediment pollutant under stationary condition is carried out. The release fluxes of different pollutions in sediment are calculated, which perfects the theory of eutrophication ecosystem dynamic model.(7) Considering the lake sediment pollutant release and point and non-point source on watershed scale influence on water quality, the sediment release flux model and non-point source model are added to the eutrophication ecosystem dynamic model to establish water bloom risk evalution model. The model can assess and forecast the level of water blooms risk, the outbreak time of water blooms and the extent of water blooms effects in the future detailedly and accurately. The assessment model provides technical support for water quality management.(8) The algal blooms risk assement method based on the biological accumulation model and the algal blooms risk evalution model based on the ecological dynamic model are used to predicte the algal blooms risk of Xikeng Reservoir, Esat Lake and the middle and downstream of Han River, respectively. The simulation results are compared between the two assessment methods.