The Spatial-temporal Variation And Pollution Assessment Of Water Quality Of Dong Yang River

To observe the pollution of Dongyang River Mainstream and tributaries-a typical watershed in Dongyang City,the water bodies in different period and space were monitored.The water quality was analyzesed and evaluated about Dongyang River,Nanjiang River and Baixi River in the past six years.The results were as follows:with the five water governance in-depth development,the contents of CODcr,NH3-N and TP had decreased in Dongyang River,which reached the maximum in 2011 and the minimum in 2016.The contents of CODCr,NH3-N and TP in Baixi River and Dongyang River showed an upward trend from upstream to downstream,reaching the maximum in Yanzhen and Yidong bridge.The contents of CODcr,NH3-N and TP showed decrease fluctuation trend from Mingde to the downstream in Nanjiang River,and Mingde reached the highest level.The Nemerow pollution index of most monitoring sections decreased gradually with time gone,and reached the lowest level in 2016.Yanxi reached the highest level in Baixi River,and the pollution factors were mainly CODcr and NH3-N.Yidong reached the highest level in Dongyang monitoring sections,and the pollution factors were mainly NH3-N.Mingde reached the highest level in Nanjiang River,and the pollution factors were mainly CODCr and NH3-N.The pollution degree of Mingde was the most serious in the Nanjiang River and the pollution factors were CODcr,NH3-N and TP.In order to understand the pollution level in the developed middle area of Zhejiang province,conventional indexs were investigated for their contents and distributions in the Dongyang River where 37 water samples in wet and dry seasons were collected.The results were as follows:the contents of CODMn in Dongyang River mainstream during wet season and Baixi River mainstream during dry season were higher than grade Ⅲ.The contents of TN exceeded the standard in the mainstream of Dongyang River,Baixi River and Nanjiang.The contents of CODMn and TN in most sections were higher in dry season than in wet season.The order of over-standard rate in wet season was:TN>TP>NH3-N>DO>CODMn>pH.The order of over-standard rate in dry season was:TN>CODMn>TP>DO>NH3-N>pH.TN,NH3-N and TP were the main influencing factors in wet and dry season.The integrated principal component analysis showed that Hudiankeng,Xixi,Qiaoxi,Banbangshan,Industrial park and Banbangshan were over the comprehensive classification of water quality classification standard(>0)in the seasons.In order to understand the pollution level in the developed middle area of Zhejiang province,seven heavy metals(Zn Cu Pb Cr Cd As and Hg)were investigated for their contents and distribution in the Dongyang River where 37 water samples in the wet and dry seasons were collected.The results were that the order about average concents of heavy metals in both wet and dry season was:Zn>Pb>Cu>Cr>As>Cd>Hg,and the average contents of Zn,Cu and Cd did not exceed the relevant standards,while the others exceeded that,whose order was:Hg>Pb>Cr>As.The change trend of Zn,Hg and Cd showed the trend of Fluctuation trend from the upper to the downstream tributaries,and the peak appeared in the industrial park and economic strong town.Chengxi and Raoxi reached moderate pollution in both wet and dry seasons.Health risk assessment showed that the level of health risks caused by chemical carcinogens was far greater than that caused by non-carcinogens.The health risk level caused by drinking water was higher than that of skin.The order of health hazard of carcinogens was Cr>As>Cd.