In Situ Remediation Of Nitrogen And Phosphorus Release From Polluted Sediments Of Urban River

Urban rivers are thought to be the symbols of one city.They are known not only for their ecological functions such as supplying water source,providing green space,protecting environment and conducting tourism,but also they are the spaces where people can take entertainment and be close with nature.With the expanding of urban population and the accelerating process of industrialization,a large number of sewage discharged into rivers.Nitrogen and Phosphorus are main pollutants.River regulation is a complex project and most of the techniques are mainly based on the ectopic repair methods such as sediment dredging,which has not only long cycle and high cost,but also has many destroy to the river ecological system and cause serious pollution again.In order to avoid the shortcomings of the traditional technology,we will use artificial simulation of polluted river channel to carry out the research on the restoration of urban river sediment.The main contents are as follows:(1)We need to build a database of major pollutants in river water and sediment,through detecting the water quality and sediment of 16 different polluted river channels in Jiaxing,so as to provide theoretical support for river sediment repair work late.(2)To studying the seasonal variation of pollutant concentrations in polluted water and sediment,and to analyzing the correlation between indexes so as to explore the implicit relationships between pollutants.(3)In this study,the composite mulching material with waste brick as the main material was applied to carry out the in situ covering technology with different cover thickness to study the remediation effect of polluted sediment.(4)In this study,submerged macrophytes,such as Ceratophyllum demersum and Vallisneria,were used as dominant plant species to carry out in situ phytoremediation of different planting densities for ecological remediation of contaminated sediments.From what has been the above research,the results show that:(1)The concentration of pollutants in water and sediment showed obvious seasonal characteristics,and the changes among pollutants correlated with each other;(2)In situ cover remediation can effectively remove nitrogen and phosphorus in water and sediment.TP and TN in the water of the purification rate were 85.71%,85.71%;TP,TN and NH3-N in the sediment of the purification rate were 83.33%,28.3%,42.4%.The greater the laying thickness,the better the effect of inhibiting the release of nitrogen and phosphorus the experiment has laid the best repair effect of covering materials 5cm;(3)In Ceratophyllum demersum,Vallisneria spiralis in situ phytoremediation materials of TN,TP and NH3-N in water purification rate were 74.62%,85.95%,87.5%,aquatic plant density is too large or too small is not conducive to the removal of nitrogen and phosphorus,reasonable planting density can effectively degrade nitrogen and phosphorus concentration,it can also achieve to maximize the use of resources?Compared with the traditional technology,the in situ remediation technology has many advantages such as less destructive,lower cost,faster efficiency to removal nitrogen and phosphorus.Through the study of in situ remediation technology,it can provide a theoretical basis for the urban river management and program development.