Investigation Of Aquatic Plant And Effect Of Its Decomposition Process On Water Quality In Shifosi Constructed Wetland

This article is based on the Shifosi Constructed Wetland, and aquatic plants as the research object, having a dynamic investigation of aquatic plants, analysising the law of wetland succession; Indoor simulation experiment of 6 kinds of aquatic plants decomposition has taken to test the changes of water quality and determine the nutrient and organic matter releasing process; According to the aquatic plants indoor simulation, combining with wetland monitoring data year by year form import to the central and the exit, to analysis the negative effects of aquatic plants on water quality.The research results have been used for the construction of Shifosi wetland ecological management, can also be references for other wetland’s establishment and management. The main contents and conclusions are as follows:(1)Using remote sensing survey and field investigation, three years field investigation had taken on wetland aquatic plants, the investigation shows an increasing tendency of aquatic plant species new species, ninety-one kinds of aquatic plants belonging to thirty-five families, seventy genera by the time of 2014, and species including wet plant, water plant, submerged plant and floating leaf plant which can be divided into roots floating leaf plants and free floating plants. Dominant species changes in the competition process, which belongs to the community succession law; Wetland ecosystem of aquatic plants is in an dynamic equilibrium, a health wetland ecological system has been formed.(2)The indoor simulation of aquatic plants decomposition in Shifosi constructed wetland shows:the floating leaf plant and the submerged plant are easy perishable, with water plants slowest, submerged plant thorough, and the more biomass the more nutrients released; pH has a strong correlation with the lifestyle (R>0.826, P<0.05), and the sediment do not affect the pH changing trend, and the tendency of dissolved oxygen of water plant different with the other two groups, plant interior structure difference is the main cause of dissolved oxygen changing; Water plant organic matter releasing process longer than floating leaf plant and submerged plant, and releasing more, the changes of nitrogen has certain relevance with carbon, and sediment does not affect the changing trend of nitrogen, but have a influence on concentration of nitrogen; The phosphorus concentration is associated with sediment and plant biomass, there is a significant precipitation and adsorption migration phenomenon on phosphorus in water and sediment; In the process of wetland management, we should reduce too much energy input in wetland system, clearing sediment out in time, preventing overnutrition of wetlands, avoiding secondary pollution to water body.(3) According to the monitoring data in 2009-2014, from import, central, and the exit, calculating the changing rate of dissolved oxygen and other six indexes removal rate, results show:the dissolved oxygen rate and removal rate of organic matter and nutrient appear negative in some years, which have a close connection with aquatic plant increasing number and types of after the construction of the wetland and plenty of residues decomposition in summer. Therefore, in order to avoid wetland aquatic plants producing negative effects, the water should be detected in real-time for mastering the dynamic change of water environment, and taking artificial harvesting and mechanical weeding according to the different ecological habit and the growth law of aquatic plants, control the vegetation coverage reasonable avoiding plant decomposition.