Effect Of Aquatic Plant Regulation On Phosphorus Cycle In Urban Lakes

Urbanization has become one of the characteristics of China’s economic development.Urban lakes,as one of the municipal ecological construction,play a role in beautifying the environment,flood regulation and storage.However,the urban lake itself is relatively closed,poor self-regulation ability,vulnerable to eutrophication,resulting in algal bloom phenomenon,green and even smelly water.Therefore,the use of aquatic plants to regulate the level of nutrients in urban water bodies,especially to reduce the content of phosphorus in water bodies,is a common method used by lake managers in recent years,but there is a lack of quantitative research on the full cycle monitoring and effect of aquatic plants in an urban lake.The representative urban lakes:Nanjing Mochou lake as a laboratory was selected.It sets up 24enclosures at the scene,a total of 6 groups set,each of four parallel processing,processing system are:control,control+N,mowing,mowing+N,aquatic plants,aquatic plants+N,a total of 9 months of synchronous monitoring.Collection and analysis of water quality and aquatic plants in different treatment systems;Phosphorus speciation was analyzed in surface sediments collected from different treatment systems.The effects of aquatic plants on phosphorus circulation in urban lakes were analyzed by means of phosphorus deposition and release in different treatment systems.The results show that during plant growth period,aquatic plants could purify and reduce the contents of TN,TP,SRP,COD_Mn and Chl.a in water,and the removal rate is over 40%,while transparency and DO could improve and increase.It can absorb and assimilate bioavailable phosphorus in sediments.The effect was proportional to the plant biomass,and P release could be reduced by up to 33%.In the plant decay stage,the death of plants leads to serious eutrophication,and the contents of various nutrients increase by 44%～754%.The bioavailable P in sediments increased by 13%～24%,the deposition and release of phosphorus increased significantly,and the flux of phosphorus increased by 60%.It is proposed that when aquatic plants are used to regulate phosphorus cycling process in urban lakes,aquatic plants play a good control effect on lake environment in the growing period,but in the plant decay period,it is necessary to clean up the decaying plants in time,otherwise the pollution degree of lakes will be aggravated and eutrophicated.