Research About The Relationship Between Suspended Sediment And Phosphorus In Flood Period Of The Three Gorges Reservoir

As the impoundment of the Three Gorges Project gets successful,the water flow condition has changed greatly in the impounding reservoir,and so the ecological system has been affected certainly as well.In recent years,water eutrophication in the reservoir has become an important research subject,it's of great significance to understand and control the content of phosphorus in the reservoir which is one of the main reasons causing the water eutrophication.Also,during a relatively special period which has been called flood duration,the concentration of water and sediment in the reservoir accounts for the vast majority proportion.Therefore,this paper is to research the adsorption rule of sediment for the phosphorus under the environment in the large flow velocity.In addition,this experiment is mainly from a perspective of the influence about the approach how sediment absorbs phosphorus,then including the effect of the grading relationship of sediment's diameter,initial phosphate concentration,sediment concentration,flow velocity and so on.The essence of this paper has been listed below:1.Collecting water sample and suspended sediment samples for many times in three different collecting points in the Three Gorges reservoir,studying relations with flow velocity,diameter of sediment,sediment organic matter and the content of phosphorus in water,and then confirming the selection of sediment's diameter in the flume experiment.The results show that flow velocity has a positive relationship with the diameter of suspended sediment,which means the slower the flow velocity,the smaller the diameter of sediment is.But the corresponding organic matter content in the sediment is higher,so the statement that gravel and particles are larger than gravel don't exist in the river.2.Analyzing the adsorption rule of suspended sediment for phosphorus by using different grading relationships of sediment's diameter,different initial phosphate concentration,different sediment concentration and different flow velocity conditions under a relatively large flow velocity.The results show that firstly the adsorption effect of sediment increases when the diameter of sediment decreases,and when different diameters of sediment coexist,there is no effect with each other in terms of sediment absorption effect.Secondly the total adsorption amount increases with the higher sediment concentration,but unit adsorption amount gets lower;the higher the solute concentration,the higher adsorption amount of unit sediment.Eventually,the increasing of flow velocity can promote sediment absorption effect in a certain range of low velocity.To the contrary,when flow velocity is large enough,the adsorption amount of sediment will be reduced because of the increase of flow velocity.3.Fitting data of the flume adsorption experiment by using different isotherms absorption curves.The results show that both Langmuir curve and Freundlich curve can fit the adsorption experiment for phosphorus very well in the fume,but the matching ability of Langmuir curve is better.4.Analyzing the content of organic matter in the sediment by adopting various collecting ways and whether the sand should be cleared.The outcome reflects that the content of organic matter in the suspended sediment obtained by nature sedimentation method using river water samples is less than the content of organic matter in the surface sediment collected by bottom sediment of the slow flow velocity area,so we can know that clear the sand simply can get rid of more than 60% organic matter in the sediment.