Analysis Of Pollution Characteristics And Countermeasures Of Nanyang Lake And Its Main Inflow Rivers

Nanyang Lake is located in Shandong Province and belongs to the superior lake of Nansi Lake.It is a multi-functional lake integrating flood control,waterlogging control,water supply,aquatic products,shipping,tourism and so on.Nanyang Lake is a water conveyance channel connecting north and south in the east route of South to North Water Diversion Project,which has important strategic significance.The south to North Water Diversion Project has put forward higher requirements for the water quality of Nanyang Lake,and the input of pollutants into the lake is the key factor to determine the water quality.Therefore,it is necessary to analyze the pollution characteristics and ecological characteristics of Nanyang Lake and its main rivers,explore the purification effect of water ecosystem on water quality,and put forward corresponding control measures on this basis.The main research contents are as follows:(1)According to the monitoring data of Nanyang Lake and its seven main rivers from 2014 to 2018,the water quality of Nanyang Lake was analyzed by using single factor pollution index method,fuzzy evaluation method,grey correlation evaluation method and principal component analysis method.The results show that the main pollutant in Nanyang Lake is total nitrogen,and there are risks of organic pollution and total phosphorus pollution.After removing or reducing the influence of total nitrogen content,the water quality of Nanyang lake is relatively good,which generally meets the category III standard of surface water environmental quality.The water quality of Si River and Liangji canal is better than that of Zhushui River,Baima River and Guangfu River,while the water quality of Zhuzhaoxin River and Xinwanfu River is relatively poor.Organic matter and total phosphorus are the main pollutants in the inflow rivers.By comparing the water quality evaluation results of Nanyang Lake,it can be seen that the inflow rivers has a direct impact on the water quality of Nanyang lake.(2)Three representative rivers,Liangji canal,Zhuzhaoxin River and Baima River,were selected from the inflow rivers,and their water ecology was investigated during the 2018 flood season.44,39 and 50 species of phytoplankton,8,9 and 9 species of zooplankton and 19,17 and 18 species of aquatic plants were detected in the Liangji canal,the Zhuzhaoxin River and the Baima River,respectively.The biomass of phytoplankton was 4630,13860 and 17290 /ml respectively,among which cyanophyta,chlorophyta and bacillariophyta were the dominant species.The biomass of zooplankton was 195,498 and 220 /L respectively,among which rotifers were the dominant species.Aquatic plants are mainly composed of angiosperms and pteridophyte,among which angiosperms take the absolute advantage.Based on the analysis of the water pollution in three rivers by using the biodiversity index and pollution indicator species,it was found that the water quality of Liangji canal and Baima River is good,which belongs to the clean type,the water quality of Zhuzhaoxin River is relatively poor,which belongs to the ?-medium pollution type.(3)The combined process scheme of "rubber dam + ecological detention pond + surface flow constructed wetland" is put forward according to the field investigation and combined with the pollution characteristics and ecological characteristics of Nanyang Lake and the main inflow rivers.In the selection of aquatic plants,the native plants with good removal effect of characteristic pollutants and strong adaptability are preferred.After analysis,the floating plants such as Trapa bispinosa Roxb,Nymphoides peltatum(Gmel.)O.Kuntze,etc.,the emergent plants such as Typha angustifolia Linn,Typha orientalis Presl,Phragmites australis(Cav.)Trin.ex Steud,etc.,and the submerged plants such as Potamogeton pectinatus,Ceratophyllum demersum Linn,Vallisneria natans(Lour.)Hara,etc.