Study On Diatom Deposition Rule And Water Environmental Impact In South-north Water Transfer Project Water Supply

Tuancheng Lake is one of the water sources of the South-to-North Water Diversion Project in Beijing.It undertakes the important task of supplying water to water plants.The water quality is good,but the siltation is serious.To better understand Tuan Cheng lake sediment source,the formation mechanism and distribution of sediment,protection from sediment endogenous release could cause the secondary pollution of water quality problems,in the south-to-north water diversion project of Beijing and Tuan Cheng lake water channel as the study area,sedimentary diatoms as the research object,the tested periodically open channel state and algae in water,water quality and the change law of time and space of algae,Assessment of water quality;The microscopic morphology,mineral composition,content and particle size of surface sediments and exogenous sediments were compared to analyze the source of sediments.The contents of total nitrogen,total phosphorus,biosilicate,total silicon and particle size of columnar sediments were determined by stratification to study the distribution characteristics of sediments.The laboratory simulation experiment of sediment release was carried out to analyze the rule of sediment release and discuss the influence of sediment release on water environment.It is expected to fill the gap in the study of sediment formation mechanism and distribution law and provide theoretical support for subsequent management.The main conclusions are as follows:(1)the overall water quality of the South-North Water Transfer Project is good,and it is basically in the category II standard of surface water.Diatom was the main species,and the population characteristics showed obvious seasonal changes.More diatoms were detected in summer and autumn,less in winter.(2)the source of the sediments is different from that of the foreign sinks.The morphology,mineral composition,content and particle size of the sediment and the foreign sink are quite different,and the two sources are different.The sediment of Nullah does not originate from the foreign sink such as the soil,the atmospheric deposition particles and the sloughing off of the canal wall,but through their own biochemical reactions to produce precipitation,resulting in silting phenomenon.(3)distribution characteristics of columnar sediments.The vertical distribution of total nitrogen was stable in general,and slightly changed in the Middle Layer,and the vertical distribution of total phosphorus was slightly lower in the surface layer than in the bottom layer The vertical distribution of biogenic silicon content was slightly higher in the surface layer than in the bottom layer,the vertical distribution of total silicon had no obvious change,and the vertical distribution of particle size showed a decreasing trend with the increase of depth.(4)the law of internal release of sediment.Under different volume of overlying water,the release concentrations of TN,TP and COD tend to balance after increasing continuously.The smaller the volume of overlying water,the greater the release concentrations of TN,TP and COD.The maximum fluxes of total nitrogen,total phosphorus and COD from dynamic experiments were 2,3.6 and 3.8 times of those from static experiments,respectively.