| Because of the eutrophication of water bodies, the growth, reproduction and population distribution of aquatic organisms not only are impacted, but also the quality of urban water supply is threaten seriously, which destroy the ecological environment of the water body system.Eichhomia crassipes has a strong adaptability to different environmental conditions. E.crassipes could normally grow in low-nutrient and nutrient-rich waters duing to great vitality and reproductive efficiency. E. crassipes that had been confirmed by researchers were the first choice for nitrogen and phosphorus removal.The simulation experiments were carried out to set up three fators of the coverage levels, nutrient concentrations and the initial amounts of E. crassipes. Experiments compared the improvement efficiency of water quality and absorption capacity of nitrogen and phosphorus on culturing E. crassipes in the different conditions, simultaneously, analyzed the changes on the populations of aquatic organisms and the release characteristics of nutrients in the sediment in the process of repairing water which E. crassipes were applied.Breeding E.crassipes could improve the physical and chemical properties of eutrophic water significantly. One of the apparent expressions was that the oxygen in water increased, the second was that the pH value oscillated between7.0-8.0, the third one was that the COD concentration was significantly reduced.The research indicated that the defoxification of were prospectively fine. Under the condition of different coverage of E.crassipes, the removal rates of TN, TP, NH4+-N and NO3--N were63.63%～90.00%,73.33%～91.11%,68.61%～86.96%and61.22%～85.11%respectively. When the coverage was60%, the removal rates of TN, TP, NH4+-N and NO3--N reached highest. Under the condition of different initial stocking rate of E.crassipes, the removal rates of TN, TP, NH4+-N and N03--N were79.78%～90.00%,71.11%～91.11%,69.78%～86.96%and68.73%～85.11%, respectively. When the initial stocking rate was4kg/m2,the removal rates of TN, TP, NH4+-N and NO3’-N reached highest. The removal rates of TN, TP, NH4+-N and NO3--N in different eutrophic water with E.crassipes were0.069～0.289mg/L/d,0.005～ 0.041mg/L/d,0.019～0.083mg/L/d and0.042～0.281mg/L/d respectively. The removal rate of nutrients indicator with E.crassipes increased with the increasing of water eutrophication degree.The results showed that E.crassipes had good absorption and enrichment on nitrogen and phosphorus in eutrophic water as well as other pollutants, making the content of nutritive proportion of nitrogen and phosphorus increasing as well as other nutrients. When the part of E.crassipes was different, there was a big difference in N and P content. The content of N was relatively high in the aboveground parts and the P was relatively high in the root parts. As far as different coverage levels of E.crassipes was concerned, the net increases of N in the aboveground parts and root parts of E.crassipes were5.37-5.85g/kg and2.62-2.85g/kg respectively. Under this optimal conditions, the net increases of P were0.37-0.50g/kg and0.73～0.90g/kg respectively. The total absorption of N and P by E.crassipes were6.51～14.11g/m2and0.95～1.74g/m respectively. Under the condition of different initial stocking, the net increases of N in the aboveground parts and root parts were5.72-6.44g/kg and2.49-3.43g/kg respectively. Under this optimal conditions, the net increases of P were0.43-0.46g/kg and0.73-0.94g/kg respectively, the total absorption of N and P by E.crassipes were5.55～12.46g/m2and0.79～1.30g/m2respectively. Under the condition of different eutrophic water, the net increases of N in the aboveground parts and root parts were3.64～15.12g/kg and1.68～8.01g/kg respectively.Under this optimal conditions, the net increases of P were0.24～1.51g/kg and0.42～2.87g/kg respectively, the total absorption of N and P by E.crassipes were4.21～30.47g/m2and0.44-4.39g/m2respectively.The results also showed that there was highly significant possitive correlation between estimation of E.crassipes and total absorption of N and P.In eutrophic water Eichhornia crassipes could reduce the content of chlorophyll and the removal rate of chlorophyll in all treats exceeded80%. With the degree of E.crassipes coverages increased, the removal rate of the chlorophyll rised. The more the initial amounts of E.crassipes were cultivated, the higher the removal rate of chlorophyll was rised. But the removal rate difference of chlorophyll between4treatments of cultivating E. crassipes were not significant. In water body, TP concentration and chlorophyll content showed a significant positive correlation, r=0.765(P<0.05). Under three experimental factors, the species, biomass and density of benthic were quite different between each treatment, but the superiority species was Limnodrilus which was appeared100%probability. Chironomuses was early tested in experimental period and Barbronias and Helobdellas appeared later in the test.Cultivating E. crassipes could play a part in the sediment substrate, characterized by the increasing water content and the reducing content of OM, TN and TP in sediments.Under the condition of different coverages of E. crassipes, the content of OM, TN and TP in sediments decreased to20.01～18.73g/kg,1.54～1.34g/kg and0.34～0.29g/kg respectively in the end of the test. The removal rates of OM in surface sediments reached by16.32%～25.67%, and the subduction gross of TN and TP in surface sediments were13.04～32.01g and3.26～6.38g respectively. Under the condition of different initial stocking rate, he content of OM, TN and TP in surface sediments decreased to21.88～18.69g/kg,1.52～1.35g/kg and0.32～0.28g/kg respectively in the end of the test. The removal rates of OM in surface sediments reached by12.13%～25.67%, and the subduction gross of TN and TP in surface sediments were14.73～25.12g and3.48-6.27g respectively. Under the condition of four different eutrophic water, the content of OM, TN and TP in sediments decreased to20.32g～19.13g/kg,1.48～1.33g/kg and0.36～0.28g/kg respectively in the end of the test, and the subduction gross of TN and TP in sediments were17.50～35.64g and2.03～6.32g respectively.The results showed that there was highly significant possitive correlation between the subduction gross of OM, TN and TP in sediments and the increasing dry matter.In summary,under the different conditions, E. crassipes could effectively improve the water quality of eutrophic water. Through the absorption and enrichment of E. crassipes, the nutrients and pollutants in water not only could be effectively absorbed by E.crassipes, but also could reduce the concentration of organic matter and nutrients of N and P. |
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