Study On The Purification Ability Of Hydrophytes To Water Environment Of Urban Lakes

Aquatic plants are critical components of aquatic ecosystem. Their successful structures made up of lake aquatic plant community, and took a great role of water purification. Two parts were dealt with in the paper. The first was the investigation to the functions of city lake aquatic plants on water purification. And the second was making a reconstruction plan for a wetland aquatic ecosystem based on a typical city wetland (Nanjing Bailuzhou Park wetland). An contrast analyses of the water qualities pre and post the aquatic plant restoration was made from experiments. The research results could make a large contribution to the conservation projects of lake and wetland in city and provide both theoretical and technical supports for water purification.In order to compare the ability of aquatic plants on water quality improvement in cities, using Xuanwu Lake, Mochou Lake and Bailuzhou Park in Nanjing as research objecte, the water purification ability resulted from effective structures of aquatic plants community were discussed in the paper according to the study of water indexes, lake silt and aquatic plant compositions. The results showed:Dissolved Oxygen (DO), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Nitrogen (TN), Total Phosphorus (TP) etc. were the main factors to reflect water pollution in urban lakes. The water quality change in a year was in the order of summer> spring> autumn> winter.At the same time and same lake but different sampling points, there were significant differences between water qualities. Water quality was usually much better where there was plant growth and a little artificial disturbance. Comparing and analyzing the purifications of communities of submerged macrophyte, floating plants and emerged plants, the results showed that submerged macrophyte had better absorption ability to TN and TP and could effectively improve water environment. There was in the order of submerged macrophyte > floating plant > emerged plant.For the collocation of communities of aquatic plants and sight rebuilding in the urban classic lake, setting Bailuzhou wetland as an example, the reasonable kinds of water plants with applications of the pre-research was choosed, and a project of the collocation of plant communities and sights rebuilding was applied by combining zoology functions of Bailuzhou wetland.