Nitrogen And Phosphorus Uptake Kinetics Of Vallisneria Natans

China is a big fishery country. The eutrophication progress of freshwater for aquaculture intensified with the increase of fishery scale and density.Frequent outbreaks of algal blooms not only result in water pollution,affecting the development of industry,but also will be a threat to the human settlement.Therefore, environmental protection and restoration of fresh water become an important technical support for the sustainable development of aquaculture.The use of aquatic plants for water repair operation is uncomplicated, more and more studies are in progress. As roots and leaves of submerged aquatic plant can absorb nutrients such as nitrogen and phosphorus in water, we can use it to achieve the purpose of water purification. But resistance of different species is different, and the same as absorption capacity of different ion forms. The water environment also has its impacts on aquatic plant, such as: pH, temperature, light and micro-organisms, and so on. This study used absorption kinetics to reveal the removal capacity of nitrogen and phosphorus by Vallisneria in different water environmental conditions to provide reference for governance of water eutrophication. The main research contents and results are summarized as follows:1Studies that wrapped root group and non-wrapped root group absorb ammonium, phosphate, nitrate, nitrite have shows that:the removal of ammonium, phosphate, nitrate, nitrite of two experimental group were significantly different from the control group, but there were no significant difference between two experimental groups. The removal rate of nitrate, nitrite, ammonium and phosphate for leaves was11.5±5.1%、30.3±4.4%、64.3±5.1%和36.3±2.6%. The removal rate of nitrate, nitrite,ammonium and phosphate for roots was2.1±0.8%、3.8±1.2%、7.6±2.8%和2.7±0.9%. So we can inference:the leave of vallisneria uptake great more these ions than root, and the leave is in the dominant place in ions absorption of whole plant.2Absorption kinetics of vallisneria for ammonium, phosphate, nitrate, nitrite shows that:the maximum uptake rate of nitrate in different condition of pH=5.5、50001ux、32centigrade was0.0050426mmol·g-1·h-1,0.0064906mmol·g-1·h-1,0.001889mmol·g-1·h-1, respectively.And it will have the maximum affinity for nitrate when the condition is pH=8.5or10000lux or12centigrade.The results indicated that:the maximum uptake rate of nitrite in different condition of pH=5.5、15000lux、32centigrade was0.015955mmol·g-1·h-1、0.015509mmol·g-1·h-1,0.015509mmol·g-1·h-1, respectively.And it will have the maximum affinity for nitrite when the condition is pH=5.5or150001ux or32centigrade.The results indicated that:the maximum uptake rate of ammonium in different condition of pH=5.5、10000lux、22centigrade was0.16898mmol·g-1·h-1、0.15491mmol·g-1·h-1,0.2084mmol·g-1·h-1, respectively.And it will have the maximum affinity for ammonium when the condition is pH=5.5or15000lux or22centigrade.The results indicated that:the maximum uptake rate of phosphate in different condition of pH=7、10000lux、22centigrade was1.2528188μmol·g-1·h-11.4494544μmol·g-1·h-1、1.5622559μmol·g-1·h-1, respectively.And it will have the maximum affinity for phosphate when the condition is pH=8.5or150001ux or22centigrade.The absorption kinetics of nitrite uptake under the effects of ammonium and nitrite show that:when ammonium and nitrite is40μmol·L-1,the maximum absorption rates were0.009838646mmol·g-1·h-1and0.008634087mmol·g-1·h-1, respectively, no significant differences in affinity.3The average uptake rate of nitrogen and phosphorus decreased with the time at same initial concentration. Excessive Vallisneria density will not improve the purification efficiency, a suitable density can maintain a high nitrogen and phosphorus absorption rate. The appropriate density of Vallisneria natans is100g·m-2, when the concentration of nitrate, nitrite.ammonium and phosphate was22.9～93.1μmol·L-1,9.3～18.6μmol·L-1,69.3～142.9μmol·L-1and11.0～25.5μmol·L-1.