Water Quality Evaluation And Pollution Control Of Yangcheng Lake

Yangcheng Lake is located in the northeastern of Suzhou,is one of the most important lakes in Suzhou,undertaking the functions of the source of drinking water,the base of the aquaculture,transportation and others.In recent years,the quality of the lake deteriorates due to the lack of unified planning and management.The phenomenon of algal bloom happened in 2013.This article evaluates the quality of recent five years of Yangcheng Lake,analyses the tendency of variety,analyses the principal components of rivers into lakes using the principal component analysis method,estimates the total amount of major pollutants through the investigation,puts forward corresponding pollutant reduction measures combined with the water environmental capacity of the Yangcheng Lake in order to protecting the water quality of Yangcheng Lake and avoiding the phenomenon of huge investment but weak effect.The conclusion of the article are as follows:(1)According to the monitoring data of Yangcheng Lake in recent five years and the analysis of tendency of water quality,the concentration of CODCr,NH3-N,CODMn of the lake descend every year substantially.The concentration of CODCr and CODMn can reach the standard of III species of quality of the surface water,the concentration of NH3-N can reach the standard of II species.But the concentration of TP and TN fluctuate largely,they cannot reach standard of III species in western and central lake,the concentration of TN can only reach inferior V species.It is polluted severely.(2)From the aspect of the region,the quality of eastern lake is best,while the western lake is worst by using the comprehensive water quality identification index and analyzing the tendency of the water quality.The quality of western and central lake can only reach IV even V species.From the aspect of the period,the quality of wet season is worse than dry season,this may because the lake is polluted by the agricultural widespread source,the rainfall is heavy in wet season,the pollutants flow into the lake with the rain.From the pollution factor,TP and TN are higher.(3)The extent of eutrophication is evaluated and analyzed using comprehensive nutrition state index(TLI),the water quality of Yangchen Lake is generally mild eutrophication,especially in western and central lake the index is higher while combining TP,TN,transparency and other index.The lake need to be treated immediately.(4)Water quality around the main river into the lake is analyzed using SPSS software and the principal component analysis method,in dry seasons,the burthen rate of NH3-N,TP,TN,and CODMn is higher in the first principal component,the burthen rate of volatile phenol is higher in the second principal component.In normal seasons,the burthen rate of NH3-N,TP,TN and CODMn is higher in the first principal component;the burthen rate of CODCr is higher in the second principal component.In wet seasons,the burthen rate of NH3-N,TP,TN is higher in the first principal component;the burthen rate of volatile phenol is higher in the second principal component.Generally speaking,the main pollutants in rivers into the lake are NH3-N,TP and TN.(5)By the method of field investigation and data access,it is calculated that 385.3t CODCr,19.6t NH3-N are discharged by industrial point source every year,858.8t CODCr,109.56t NH3-N,11.5t TP,155.6t TN are discharged by domestic sewage every year,19.5t TP,277.1t TN are discharged by aquiculture every year,4.8t TP,113.5t TN are discharged by agricultural cultivation wastewater every year.The pollutants into Yangcheng Lake are mainly caused by widespread pollution.In various agricultural activities,the amount of pollution discharged by aquaculture is the largest,account for nearly 50%of the entire widespread pollution.The second is the domestic sewage.(6)Estimating the environment capacity of Yangcheng Lake by Vollenweider model and Dillon model.Taking ? species of quality of the surface water as the standard,the environment capacity of CODCr is 107354t/a,the environment capacity of TP is 268t/a,the environment capacity of TN is 2878t/a.(7)According to the total amount of pollutants estimated,different pollutant reduction measures are put forward according to different pollution resources.