Study On Eutrophication Evaluation And Nutritional Status In Backwater Area Of Yulin River

The Three Gorges project is mainly to conduct the flood control,with the function of shipping,water supply and so on,but the construction of the Three Gorges project destroys the ecosystem structure and function,which leads to the deterioration of the water quality in the reservoir area.With the periodical storage and discharge process of the Three Gorges Project,the influence of backwater of the reservoir area makes the hydrodynamic conditions change,the decrease of water flow rate and the increase of retention time,resulting in more easily and more transparency of sediment deposition,creating conditions for the outbreak of Algal bloom.Therefore,the thesis takes the Yulin River as the research object,including the nutrient state and changing regularity of the Yulin River and probes into the effect of sediment on the growth of phytoplankton,and mainly studies the mechanism of the sediment's influence on the shading and nitrogen-phosphorus adsorption kinetics.Moreover,the paper preliminarily analyses the feedback effect of algae secretion on sediment flocculation.The main content and research results of this paper include the following:(1)The water quality of Yulin River is in nutrient-mild nutrition,February to March is the worst time for the Yulin River's water pollution,followed by July-August.The eutrophication was poor.Using nutritional status index to evaluate the eutrophication state of the river water body,combining its evaluation results,the main reasons of this situation are analyzed,and the comprehensive preventive measures should be adopted to rectify and protect the environment of the reservoir area.(2)Consult the relevant water quality information,to conduct the PCA analysis and Pearson correlation coefficient on the estuary of Yulin River,Paihua,Shu Jia waters field of various environmental factors,indicating that total nitrogen,total phosphorus,water temperature,flow rate and suspension are the environmental factors affecting chlorophyll.The total nitrogen,total phosphorus and water temperature were positively correlated with the content of chlorophyll a,and the velocity and suspension were negatively correlated with the content of chlorophyll a.(3)The two adsorption kinetics models of pseudo-level and pseudo-two were introduced,aiming at the current regularity of sediment adsorption nutrients.The kinetic tests on nitrate nitrogen,phosphate and ammonia nitrogen adsorbed by sediment were designed with the initial concentrations of sediment content and nitrate nitrogen,phosphate and ammonia nitrogen.The results of the study were: under the same conditions,the unit mass sediment was nitrate nitrogen.The equilibrium adsorption capacity of phosphate and ammonia nitrogen was negatively correlated with sediment content,and was positively correlated with nitrate nitrogen,phosphate and ammonia nitrogen initial concentration;pseudo two-level kinetic equations can well describe the behaviors of nitrate nitrogen,phosphate and ammonia nitrogen adsorbed by sediment.(4)In the Isothermal equilibrium adsorption test,the effects of nitrate nitrogen,phosphate and ammonia nitrogen on different initial concentrations and sediment content were investigated,and the equilibrium adsorption capacity and adsorption isotherm of nitrate nitrogen,phosphate and ammonia nitrogen were studied.The study shows that the unit mass sediment has the nitrate nitrogen.The equilibrium adsorption capacity of phosphate and ammonia nitrogen was positively correlated with nitrate nitrogen,phosphate and initial concentration of ammonia nitrogen,and the sediment content was negatively correlated;the isothermal adsorption process of nitrate nitrogen,phosphate and ammonia nitrogen satisfies the isothermal adsorption model of Langmuir,Freundlich and Freundlich respectively.(5)In the study of flocculation effect of sediment and algae,the particle size and IR spectra of flocculation were tested.The study shows that the sediment D(0.5)is 19.119 um,the algae D(0.5)is 8.356 um,and the sediment and algae's flocculation of the largest particle size is 33.257 um greater than the sediment and the algae add,the interaction between sediment and algae is illustrated,and the interaction between algae and sediment is found by IR spectra,because the extracellular polymer C= key or-OH or-NH and sediment occurrence of algae surface are combined with flocculation.