Phytoremediation Technology Of Aquatic Plants In Controlling Cyanobacteria Bloom In Water Body

Urban park landscape water is shallow lakes,with slow,poor mobility and quite static,and urban water nutrient content is high,in the appropriate temperature and climate environment,which is easy to produce algae water blooms and can not meet the requirements of landscape water.In order to reduce the phytoplankton in landscape water and ensure the quality of water environment and the restoration of landscape,the use of aquatic plants remediation technology to control algal bloom is of great significance.This research takes Beijing city Park-Yuyuantan Park as an example,with the help of the existing lake area of Yuyuantan Park,the selection of two lakes named Beimen and Xinjian,as the study objects of plant planting technology,and the other lake bodies themselves also have different types of aquatic plants as comparison.The measures taken in the Beimen Lake are to be grown with Nelumbo nucifera,Acorus calamzts,Scirpus tabernaemontani,Myriophyllum spicatum,Najas marina and Najas minor.The measures taken in Xinjian Lake are the collocation of plant with Nelumbo nucifera,Acorus calamus,Scirpus tabernaemontani,Arundo donaxt Lythrum salicaria,Thalia aealdata,Myriophyllum spicatum,Najas marina and Najas minor.And according to the city park water specific to the hard bottom of the lake,we put forward a targeted planting methods.Along the lake to build a planting pool firstly,the emergent plants can be grown into the planting pool,and submerged plants planted in pots,then directly sank into the water.During the period from 2015 to 2017,regular monthly monitoring of water bodies in Yuyuantan Lakes was carried out to study the changes of algae and water quality before and after the aquatic plant planting technology.The content of chlorophyll a,b and c,the species of algae and the density of algae cells were measured,and the changes of water temperature,pH value and DO(dissolve oxygen),as well as TN(total nitrogen),TP(total phosphorus),COD(chemical oxygen demand),NH3-N(ammoniacal nitrogen),transparency and fluorescent substances were monitored.The results showed that the repair effect was more significant in the second year of 2017,when the aquatic plant was repaired.In the summer of 2017,there were no aquatic plants in Dahu with Chlfa content as high as 65.1 ?g/l,while the Beimen's Chla content only for the 6.2?g/L and the Xinjian's Chla content is only 11.3?g/L.In 2015,the water temperature,pH values and the concentrations of DO,TN,TP,COD and NH3-N were 3.4-29.6?,6.12-9.61,4.06-13.67 mg/L,0.17-1.86 mg/L,0.020-0.292 mg/L,17.7-49.8 mg/L and 0.036-1.120 mg/L,respectively.In addition,the water quality and transparency were improved,the water was clear and transparent,the nitrogen and phosphorus content was lower,and the effect was better than the lake containing only the water plants,indicating that submerged plants played a major role in algae control and water quality improvement.In 2017,the water temperature,pH values and the concentrations of DO,TN,TP,COD and NH3-N were 2.8-34.1?,7.47-9.41,6.18-21.70 mg/L,0.53-1.12 mg/L,0.026-0.128 mg/L,10.6-60.6 mg/L,and 0.020-0.428 mg/L,respectively.The fluorescent substances in water were detected by three-dimensional fluorescence spectrometry,and the submerged plants could secrete the substances,which were in the humic acid region and were seasonal.