Study On The Construction And Efficacy Mechanism Of Aquatic Vegetation System For Algal Bloom Inhibition And Water Purification

At present,Baiyangdian waters are characterized by low concentrations of dissolved oxygen and high nutrient salts,and the phenomenon of eutrophication is serious,and the outbreak of algal blooms occurs frequently.In order to improve the water quality of Baiyangdian Lake and realize the ecological restoration of the natural wetlands in the lake,it is of great significance to control and restore the eutrophic water.In this study,Zaozha lake surface in Baiyangdian area was selected as the research object,and the microalgae community and water ecological environment in the local water body were investigated.The results showed that the eutrophication was still serious in this area,the water quality was in poor V level.Besides,the proportion of blue-green algae in the microalgae community was large,the density of algae was various in different waters,and the risk of bursting out water blooms was very high.According to the status quo of water quality of Zaozha lake,the effects of submerged plants on water quality and microalgae community were studied,which provided data support for ecological management in the area.In addition,the screening methods of aquatic plants suitable for algal blooms inhibition and water purification were summarized and established,and the aquatic vegetation system was constructed.Finally,the species and density of microalgae and the changes of TN,TP,NH4'-N and COD in different densities of microalgae communities under the background of dominant plants,namely Ceratophyllum,were determined.The results showed that the removal efficiencies of TN and COD by Ceratophyllum with low-density microalgae below 2�104 cell/mL were better than those under the same dominant plant with high-density microalgae.Through consulting relevant data,16 points about aquatic plants in four aspects of plant properties,growth environment,economy and bioactive substances were summarized.According to Baiyangdian's geographical location,water quality characteristics,ecological conditions,engineering needs and basic conditions of the site,three submerged plants,Ceratophyllum,Vallisneria and Elodea,which are suitable for Baiyangdian water remediation and research,have been screened many times.Under different microalgae densities in water environment,the removal efficiency of TP in each experimental group was not significantly different.The removal rates of NH4+-N in different water bodies with different microalgal densities were all above 85%,much higher than that in the control group with the presence of Ceratophyllum.At the same time,the population structure of microalgae community was studied under the existence of Ceratophyllum.The results showed that such as Coelosphaerium,Chroococcales,Phormidiaceae,and Anabaena sp.would evolve to be dominant species in phytoplankton in the later stage of each experimental group,and their proportion of phytoplankton in the microalgae community would increase,and the water quality would be gradually improved.To study the effects of different combinations of submerged plants on the aquatic environment and physiological changes of plants at different temperatures.The results showed that among the plant combinations based on Ceratophyllum,the combination of Ceratophyllum+Elodea had the best effect on pollutant removal at different water temperatures.Compared with other experimental groups,the removal rate of COD and TN in the Ceratophyllum+Elodea was the best at 250C,and the removal rate of NH4--N was second only lower to the combination of Ceratophyllum+Vallisneria,while the removal rate of TP was second only lower to the combination of Vallisneria+Ceratophyllum+Elodeay under long-term low temperature(non-icing),the photosynthesis efficiency of Vallisneria and Ceratophyllum will gradually decrease,and Elodea has higher resistance to low temperature,the Ceratophyllum+Elodea combination is theoretically considered to be the best for managing the water environment in Zaozha Lake area.In summary,this study summarized the plant selection methods for aquatic ecological restoration,and conducted a systematic and comprehensive experimental study on the microalgae community,water quality indicators and physiological changes of plant combinations at different temperatures under the background of Ceratophyllum in Zaozha Lake.The results provided a theoretical and data basis for the ecological restoration of Zaozha lake.