Contribution Of Atmospheric Deposition To Nitrogen And Phosphorus Pollution Load Of Lakes And Effects Of Different Combinations Of Submerged Plants On Water Purification

The lake ecosystem is an important part of the aquatic environment.Pollution control of lakes and ecological restoration of polluted lakes have become hot issues of lake ecosystem management.Previous studies on lake pollution sources and pollutant control mainly focused on direct pollution caused by human production activities,such as point source pollution,non-ponit source pollution,and internal source pollution.However,few studies have conducted to study the nitrogen and phosphorus deposition from atmospheric deposition in urban lakes.For ecological restoration of damaged lake ecosystem,the method of planting aquatic plants has been widely used,and the current planting strategy mainly plant a single plant in large area,but the application of different combination of submerged plants for ecological restoration is rarely used.in order to provide technical information for urban lake management,the contribution of atmospheric deposition to nitrogen and phosphorus pollution in urban lake was explored by collecting and measuring the content of pollutants in the precipitation of East Lake.In addition,this study also used different combinations of submerged plants to treat eutrophic lake water,in order to explore the effect of different plant combinations on water quality purification.The main findings are as follows:（1）During the observation period,the concentration of TN,TP and NH₄⁺-N carried by atmospheric deposition varied greatly,but three pollutant concentrations present similar change patterns.For seasonal pattern,the three concentration of pollutants caused by atmospheric deposition is higher in autumn and winter,and lower in spring and summer.Regression analysis showed that no obvious pattern of three concentration of pollutants with time were observed.（2）The annual deposition load of TN,TP and NH₄⁺-N carried by atmospheric deposition in Wuhan East Lake is 76.94t,4.61t,and 31.83t,which take up 7.28%,4.41%and 7.61%to the total TN,TP and NH₄⁺-N pollutants of East Lake,respectively.（3）Variance partition analysis showed that compared with air particulate matter,meteorological factors were the main factors that affect the pollutant contribution of the East Lake.The independent effects of meteorological factors for TN,TP and NH₄⁺-N deposition fluxes were 11.01%,0.95%and 10.92%,respectively.Correlation analysis showed that rainfall,PM_2.5 and PM₁₀ had significant positive correlation effects on atmospheric TN,TP and NH₄⁺-N deposition load,while relative humidity had significant negative correlation effects on atmospheric TN,TP and NH₄⁺-N deposition load.（4）The removal experiments of TN,TP and NH₄⁺-N by plant combinations showed that the concentration of TN,TP and NH₄⁺-N in each plant group changed significantly with time,expect for the TN of Vallisneria natans+Myriophyllum spicatum group.Also,different change pattern were observed among the different plant combinations.（5）For removal efficiency of TN,TP,NH₄⁺-N,various submerged plant combinations had significant purification effects on polluted lake water,but different submerged plant combinations had different removal effects on TN,TP,NH₄⁺-N purification efficiency.The Vallisneria natans+Hydrilla verticillata group had the best removal effect on TN and TP,with removal rates reaching 71.27%and 89.73%respectively;the Myriophyllum spicatum group had the best removal effect on NH₄⁺-N,with removal rate reaching 95.24%.（6）Redundancy analysis and multiple regression analysis showed that the TN,TP,NH₄⁺-N concentrations in the experimental system were significantly negatively affected by p H,dissolved oxygen,and total biomass.