Water Purification Function Of Two Kinds Of Submerged Plants And Their Influence On Phosphorus In The Rhizosphere Sediments

Using water and sediment of Nanhu Lake, Wuchang of Wuhan City, we designed a group pot experiments including a control and some treatments that to apply exert phosphorus by 100mg/kg to the sediment. Submerged macrophytes Potamogeton crispus, Elodea nuttallii and their mixture were planted in the sediment.From September 15, 2007, after 160 days observation, these three kinds of treatments all caused total phosphorus, total nitrogen, and content of chlorophyll a in the overlying water obviously reduced. The effect of Elodea nuttallii on the total phosphorus was better than other two treatments, and all of three treatments on controlling chlorophyll a (Chla) in high phosphorus of the sediment were more efficient than thoes in the low-phosphorus in the water. The concentration of the total soluble phosphorus in overlying water responded to the sediment with high phosphorus content reduced obviously, but it did not change significantly in the sediment with low phosphorus. In the submerged macrophytes cultivation experiment, whether or not applying phosphorus to the sediment the change of Chla along with cultivated time of the plants could be fitted better with the first order kinetic equation, and the content of Chla in overlying water could be controlled by the submerged macrophytes.The detail results are:(1) Using aquatic plants in high phosphorus environment was very effective to control TP of overlying water. It was especially in the growth of the late to control TN, Chla content;(2) Potamogeton crispus, Elodea nuttallii made the Fe-P contents of the sediment more higher than the natural station, and in high-phosphorus environments became more evident, the latter dropped to the level of the natural station; For submerged macrophyte Elodea nuttallii of short-term, the content of high Fe-O-P of the sediments was significantly decreased but no effect for long-term;(3) There was a significant positive correlation between TDP, TP content of the overlying water and content of calcium-bond-iron phosphorus and Fe-O-P of sediment, especially for Potamogeton crispus planted alone or Elodea nuttallii planted sediment of the Ca₁₀-P changes,which had the good correlation to the overlying water in phosphorus;(4) There was no significant differences from phosphorus content of the plant whether in the winter or in the spring, and as the phosphorus of the sediment increased, phosphorus content of both macrophytes showed significant differences in the nutritional status of the sediment, which affected the accumulation of phosphorus in plants;(5) There was a significant negative correlation of phosphorus contents between aquatic macrophytes and water environment in Nanhu Lake, It was harm to submerged macrophytes in higher phosphorus concentrations of overlying water,but Elodea nuttallii was more adapted to the high degree of eutrophication of overlying water, sometimes,the eutrophication of water bodies was a stress to aquatic macrophytes.