Dynamic Monitoring And Improvement Of Yuanmingyuan Water Ecological Restoration

At present,many lakes at home and abroad are facing eutrophication of water bodies to varying degrees.The Yuanmingyuan Garden has been using reclaimed water as a supplemental water source since 2007.Although it effectively solves the problem of water resource demand,it is more likely to cause eutrophication.Currently,there are many methods for water body restoration.Among the many restoration methods,the submerged plant-based restoration method has low cost and good ecological effect.However,excessive growth of submerged plants will cause secondary pollution of the water body,so proper harvesting is essential.According to the Yuanmingyuan field survey,it is known that the annual labor cost for plant harvesting is expensive,and through the reasonable control of submerged plants,research to further reduce labor costs is also an urgent problem that needs to be solved.In view of the above problems,this paper studies the purification effect of submerged plants in the Yuanmingyuan Lake area on water quality,the diversity index of plankton in water bodies,and the pollution status of heavy metals in sediments.Based on field studies in the lake area,and in view of the problems of manual control,experiments were conducted at the experimental base to study the effects of harvesting on the growth rate of submerged plants and the effects of different harvesting cycles and depths on water quality and heavy metals in sediment.It not only clarifies the current state of aquatic ecological restoration in Yuanmingyuan,but also improves it on the existing basis,providing research references for the use of recycled water and the maintenance of aquatic environment.The main research contents of this article are as follows:(1)Through field investigation,it was found out that the existing submerged plants in Yuanmingyuan mainly include 12 and 5 dominant species;Data analysis of water quality showed that: the TP concentration drop rate reached 85.71%;the TN concentration drop rate reached 59.73%;the NH3-4 concentration drop rate reached 62.5%,and the COD concentration increase rate reached 6.58%;chlorophyll a remained basically at 9.32 mg/L Lower level.Zooplankton species in the lake area are mainly rotifers,of which Anuraeopsis fissa and Polyarthra trigla are the dominant species in the entire lake area;phytoplankton is mainly Chlorophyta and Achnanthes exigua is the dominant species;based on 14 sampling points,2 closed points were selected The water body implements two modes of large scale community patch planting and small community scale hybrid planting for ecological restoration,and analyzes its water purification effect: the water purification effect of large scale community patch planting compared to small community scale hybrid planting method better.(2)Through the harvesting experiments of three submerged plants,it was concluded that the submerged plants had a growth rate of 1-3(cm / d),a harvesting period of 20 days,and a harvesting depth of 12 cm.The plant growth rate was the smallest.And the removal effect of nitrogen and phosphorus was the best under this harvesting scheme,the removal rate of nitrogen reached 90.79%,and the removal effect of phosphorus reached 93.36%.Potamogeton pectinatus L has the best effect on reducing heavy metals in the eighth,which is more than 1.5 times the reduction effect of Myriophyllum verticillatum L(of which zinc and chromium are about 4 times),and about 1.1 times that of Ceratophyllum demersum L.