| The core of lake ecological restoration technology is submerged macrophyte community restoration technology.In response to a series of problems,such as the deterioration of the ecological environment of the water body in Baiyangdian,Hebei,it is necessary to repair submerged macrophytes in its waters.This study conducted a survey and analysis of the changes in the submerged macrophytes in Baiyangdian Lake over the years and the status quo in 2018,in combination with the special properties of submerged macrophytes,we selected submerged macrophytes species suitable for Baiyangdian Lake;studied different water periods(high water period,level period,withered water period).The Relevance between submerged macrophytes and water quality and sediment environmental factors determined the key environmental factors affecting submerged macrophytes;through the monitoring of the underwater light field in the Baiyangdian District and calculating the depth of light compensation of submerged macrophytes populations and communities in the target waters,and establish the relationship between the depth of light compensation of submerged macrophytes and transparency.Evaluation of the Baiyangdian District to determine the appropriate area for submerged macrophytes restoration.The submerged phytoremediation technology in baiyangdian lake was established based on the underwater light field and macrophyte characteristics,combining the characteristics of the remediation area to optimize the repair plan.The main conclusions are as follows.(1)This study conducted four submerged macrophytes surveys in Baiyangdian Lake District in December 2017,April 2018,July 2018,and November 2018,and analyzed its historical evolution based on frequency and advantages degree,combined with the analysis of submerged macrophytes characteristics(fouling resistance,water purification ability,adaptability to the environment and method for macrophytesing),screened and determined 7 submerged macrophytesrestoration species,and carried out staged restoration:The first stage of macrophytesing species with high pollution resistance(Ceratophyllum+P.pectinatus+Myriophyllumspicatum);the second stage adds species with moderate dirt resistance(Hydrillaverticillata+Vallisneria)and sensitive species on the basis of the first stage(Najasmarina+UtriculariaaureaLour).(2)Determine the habitat factors that affect the restoration of submerged macrophytes in Baiyangdian Lake area by studying the relevance of submerged macrophytes with water quality and sediment environmental factors in different water periods(high water period,level period,withered water period).Summarizing and comparing,it can be concluded that the main water bodies and sediment environmental factors affecting submerged macrophytes are different in the three water periods of High water period,level period and withered water period.The water environmental factors that have the greatest impact on submerged macrophytes in level period,high water period and withered water period are(NO3--N,TP,and ZSD/ZM),(NH4+-N and Chl.a),ZSD/ZM.The environmental factors of sediments that had the greatest impact on submerged macrophytes in the level period,high water period and withered water period were NO3--N,TOC and IP.It shows that submerged macrophytes are obviously affected by nutrients,chlorophyll and transparency(underwater light).(3)A survey was conducted on the underwater light field in the Baiyangdian District in March and May 2019,and it was found that the underwater light attenuation coefficient was higher in May 2019 than in March 2019,and the spatial distribution of the light attenuation coefficient was east The trend from low west to high is consistent with the spatial trend of Chl.a and TSS.The high value area exists in the area with more artificial interference,while the low value area has less artificial interference.A linear relationship model between the depth of light compensation and transparency of submerged macrophytespopulations(communities)was established,revealing that Chl.a and SS had a significant effect on the depth of light compensation,and put forward effective methods to reduce Chl.a and SS,Adding 5%clay can quickly and effectively reduce Chl.a and turbidity,and reduce the content of nitrogen and COD in water.Clam culture can stabilize the water quality.(4)Use two evaluation indicators(Qi and LOI)to judge the suitable area for the first-stage restoration of submerged macrophytes in Baiyangdian Lake area,and discover the underwater light field and bottom sediment properties Common impact assessment results.Established and optimized a submerged macrophytes restoration plan:first,through evaluation to determine the appropriate area for submerged macrophytesrestoration,based on the historical status of Baiyangdian submerged macrophytes species survey and selected submerged macrophytescharacteristics;second,for low transparency Suitable for remediation area,improve water transparency through measures such as 5%clay addition or cage mussel purification;for recoverable area,analyze water depth distribution,habitat characteristics and pollution status of remediation area,and optimize target species on the basis of the first step;Third,the light compensation depth of the submerged macrophytespopulation(community)and the linear relationship model of transparency can be used to calculate the light compensation depth of the repaired community.When the light compensation depth of the submerged macrophytes population(community)≥ actual water depth,it can be repaired and macrophytesed.When the water quality gradually improves due to the existence of the pioneer species,the second stage of moderate pollution-resistant species and sensitive species should be macrophytesed at a suitable time to repair submerged macrophytes The community is composed of a relatively single and full of instability,and gradually transitions to a stable community with diversity. |
PDF Full Text Request