Purifying Effect And Mechanism Of Hydrophytes In Eutrophic Water

The status of Chinese eutrophic water is very severe: the ratio of eutrophic water increases every year, and eutrophication degree intensifies continuously. Due to their good purifying ability, ecological effects, landscape value and potentially economic value, hydrophytes have prosperous future in treating eutrophic water. Theoretical and technical supports were provided by indoor experiments on using hydrophytes to restore eutrophic water. Purifying effect of Jussiaea stipulacea Ohwi, a native kind of hydrophyte in Taihu Lake Basin, were comparatively stutied in eturophic water. And its purifying mechanism on nitrogen and phophorus were discussed through mass balance. Last, purifying ability sequences of 32 kinds of hydrophytes in eutrophic water were compared. The main conclusions are as follows:In summer, 0.119 mg Nand 0.014 mg P can be removed by per gram of Jussiaea stipulacea Ohwi per day, which are 1.6, 1.9, 2.8 times and -0.3, 0.9, 4 times greater than those of Eichhornia crassipes (Mart.) Solms.,Alternanthera philoxeroides(Mart.)Griseb., and control(unvegetated), respectively. In winter, 0.025 mg N and 0.003 mg P can be removed by per gram of Jussiaea stipulacea Ohwi per day, which are 4 times and 1 times greater than those of control. Jussiaea stipulacea Ohwi also has good removal effects for ammonia and nitrite.In winter, the contribution rates for TN removal in studied water with Jussiaea stipulacea Ohwi are Microorganism in natural water(70.8ï¼…), Increased microorganism due to the existence of hydrophyte(12.8ï¼…), Hydrophyte metabolism(18.0ï¼…), Hydrophyte adsorption(1.4ï¼…), Sedimentation(0.5ï¼…), and Hydrophyte storage(-3.2ï¼…). The contribution rates for TP removal are Increased microorganism due to the existence of hydrophyte(60.9ï¼…), Microorganism in natural water(30.5ï¼…), Hydrophyte metabolism(20.6ï¼…), Sedimentation(8.3ï¼…), Hydrophyte adsorption(6.6ï¼…)and Hydrophyte storage(-9.4ï¼…). The removal mechanisms of TN and TP in summer were also estimated.Besides, Purifying ability sequences on TN, TP, NH₃-N, NO_X-N, TP, RP and Chl-a of 32 kinds of hydrophytes were calculated, as well as Adaptability sequence, Transpiration rate sequence, Oxygen enrichment ability sequence. In the whole experiment period, the contribution rates of hyrophytes were 3.3ï¼…and 5.6ï¼…on TN and TP removal in water, and 17.5ï¼…and 18.2ï¼…on TN and TP removal in the whole system. The contribution rates of algae were 55.6ï¼…and 38.9ï¼…and the rates of gravels were 11.7ï¼…and 25.2ï¼…on TN and TP removal in water.