Study On Elodea Densa (Planch.)Casp. About The Removal Of Nitrogen And Phosphorus In Water And Its Alga-inhibiting Effects

Eco-system restoration and Water environmental quality improvement have received more and more attach importance both home and abroad. Aquatic vascular plants were the primary producer in water, the environmental effects produced by them were provided basis for the foundation of Water environmental quality improvement. This thesis is around removal effect of submerged plant Study on Elodeadensa(Planch.)Casp. about the removal of nitrogen and phosphorus in water and its alga-inhibiting, and it involved following aspects: ONE、Removals of nitrogen and phosphorus in the water by different aquatic plant.(1) We studied three kinds of submerged plant including Elodea densa(Planch.)Casp., Mayaca fluviatilis and Cabomba Fanwort. They were highly efficient in removing total nitro-gen (TN) and total phosphor (TP) at the different nutritional levels. The nutritional levels were mesotrophic concentration, eutrophic concentration, hyperbolic concentration and stress con-centration. The research results indicate:①Three kinds of submerged hydrophytes were capa-ble of removing nitrogen and phosphorus effectively at the different nutritional levels in the water;②The study found Elodea densa (Planch.) Casp. can grew normally at the different nutritional levels. Removal ability of Mayaca fluviatilis and Cabomba carliniana showed de-crease. The leaves of Mayaca fluviatilis turned yellow, the some leaves of Cabomba carliniana loss, the water quality got worse at the stress concentration.③Contrast the removal of nitrogen and phosphorus in the water with three submerged hydrophytes at the different nutritional lev-els in the water find that Elodea densa(Planch.)Casp are able to remove total phosphorus quickly. Especially, at the hyperbolic and stress concentration levels, On the fourth day,the removal percentage by Elodea densa(Planch.)Casp. were78.8%,55%in TP respectively; the removal percentage by Mayaca fluviatilis and Cabomba carliniana were24.9%26%and35%,23%in TP respectively. On the twelfth day, the removal percentage by Elodea densa (Planch.) Casp. got to100%in TP respectively; the removal percentage by Mayaca fluviatilis and Cabomba carliniana were62%,53%and44%,37%, Thus, Elodea densa (Planch.) Casp. showed strong adaptability to the environment and nitrogen and phosphorus removal notable features, especially, the characteristics of Elodea densa(Planch.)Casp. to the removal of TP were the speed of removing is fast, removal of large amount, strong ability to stress resistance.(2) Study on removals of Nitrogen and Phosphorus in Eutrophic Water by Elodea den-sa(Planch.)Casp. and Eichhornia crassipes. The results showed that:①Elodea densa (Planch.) Casp. and Eichhornia crassipes can remove nitrogen and phosphorus nutrients in Eutrophication concentration conditions. Elodea densa(Planch.)Casp. can absorb large amounts of nitrogen and phosphorus in Eutrophic Water, but the amount of increase of biomass is small.②Elodea densa(Planch.)Casp. had removal efficiency of Nitrogen and Phosphorus in the water far better than water hyacinth. TWO、 Removal ability of TP at the different phosphorus nutritional levels by Elodead-ensa(Planch.)Casp. The phosphorus nutritional levels were1.2mg/L、2.4mg/L、3.6mg/L、7.2mg/L、4.4mg/L.The results show that:①Elodea densa (Planch.) Casp. were capable of removing total phosphorus effectively at the different nutritional levels in the water. Espe-cially,when phosphorus nutritional levels were7.2mg/L, Elodea densa(Planch.)Casp. has smaller amount of biomass increased and phosphorus removal significantly and so on. when phosphorus nutritional levels were14.4mg/L, Elodeadensa(Planch.)Casp. was able to grow normally and it showed well removal efficiency.②The characteristics of Elodea densa (Planch.)Casp. to the removal of TP were the speed of removing is fast, removal of large amount and so on.The above research shows that, the characteristics of Elodea densa(Planch.)Casp. to the removal of TP were the speed of removing is fast, removal of large amount and well removal efficiency and so on. THREE、Study about the algae inhibiting effect of Elodeadensa (Planch.) Casp. hydroponic liquid and the effect of inhibiting algae by Elodeadensa (Planch.) Casp.(1) Determination and Analysis of allelochemicals in Elodea densa (Planch.) Casp. hydroponic liquid. The results showed that:①Detection of Elodea densa (Planch.) Casp. hydroponic solution containing the algal composition were:2-ring propylene-butane、 3,5-dimethyl-1-hexene、2,2,4-trimethyl-3-pentanone、2,4,6,7-four methyl heptane、1,3-dioxolane、Tridecane、2-N-pentadecyl-dioxolane、3,7,11-trimethyl-tridecaneand so on.②Preparation of14liters of Hydroponic culture fluid by200g Elodea densa(Planch.)Casp., and study the allelopathic algicidal effect.The results show that:Elodea densa (Planch.)Casp. own allelochemicals have well removal effect to the cyanobacteria on the Di-anchi Lake. During the period68days experimental,the14th day, the amount of chlorophyll with cyanobacteria in the hydroponic solution, and the amount from the initial0.5g down to0.24g. The56th days,the amount of chlorophyll with cyanobacteria in the hydroponic solution has become zero, Cyanobacteria used in the experiment all died,and sinking to the bottom of the container. The study results can provide a theoretical basis for research and development environment-friendly bio-algaecide.(2) Study the allelopathic algicidal effect to the cyanobacteria in Dianchi Lake by Elodea densa (Planch.)Casp. Research found that the characteristics of Elodea densa(Planch.)Casp. to the removal of TP were the speed of removing is fast, removal of large amount and well re-moval efficiency and so on. Phosphorus is the limiting factor for algae growth. Through static simulation test,we study the allelopathic algicidal effect by Elodea densa (Planch.)Casp.. The experiment through controlled trials and water temperature is10-15℃. During the period68days experimental, the40th day,when the amount of TP were down to0.3mg, cyanobacteria began to death,the amount of algae chlorophyll is reduced from0.5g to0.27g. Sixty-eight days, the amount of TP in the water tends to zero, the amount of algae chlorophyll has been reduced to0.01g. The results showed that, Elodea densa(Planch.)Casp. has well growth inhibition of cyanobacteria in Dianchi Lake,its provides a technical basis for Elodea densa (Planch.) Casp. used in the ecological management of eutrophic water.(3) The results show that:Elodea densa(Planch.)Casp. can inhibit the cyanobacteria growth,its may be due to make water fast phosphorus deficiency and the release of allelochemicals in water together.