Characteristics Of Eutrophication And Assessment Of Heavy Metal Pollution In The Middle And Upper Reaches Of Taojiang River

In this paper,take the upper and middle reaches of Taojiang river as the research object.According to the hydrological characteristics and the cultural characteristics of the rive,laid 45 monitoring points in the main stream and tributaries of the Taojiang river where included Xiaomu river,Tianzhai river,Huangyuncun river,Huangtian river,Dayi river and Longxing river.Collected the overlying water and sediment in June 2017?wet season?,October 2017?flat-water period?and January 2018?dry season?respectively.The contents of total phosphorus?TP?,total nitrogen?TN?,chemical oxygen demand(COD_Mn),Chlorophyll-a?Chl-a?,heavy metals Cu,Pb,Zn,Cr,Cd,Hg,As,W in overlying water and contents and forms of heavy metals Cu,Pb,Zn,Cr,Cd,Hg,As,W in sediments,were determined.Then,take the average value of three samples for analysis.The results of the analysis were as follows?1?The average values of pH,COD_Mn,TP,TN and Chl-a in the upper reach of Taojiang river were 6.91,16.1 mg·L^-1,0.076 mg·L^-1,2.01 mg·L^-11 and 0.026 mg·m^-3.According to Person's correlation analysis,TP,TN,and Chl-a are significantly correlated with each other.Further factor analysis showed that TP,TN,and Chl-a were affected by human influence and pH was influenced by nature,COD_Mnwas influenced by human and natural factors.With reference to Jin Xiangcan and Shu Jinhua's eutrophication criteria.Using fuzzy clustering analysis in fuzzy mathematics,a eutrophication evaluation model for water bodies was established.Through calculation,it was known that Longxing river belongs to middle nutrition,and Tianzhai river,Huangyuncun river,Huangtianjiang river,Dajishan river and Taojiang river were mildly nutritious.Xiaomu river was moderately eutrophic.?2?The average contents of Cr,Cu,Zn,As,Cd,Hg,Pb,W in the overlying waters of the upper and middle reaches of Taojiang river were 0.0008,0.12,0.14,0.002,0.01,0.0006,0.05,0.00002 mg·L^-1.According to Person's correlation analysis,there were similar geochemical characteristics between Cr,Cu,Zn,As,and Pb,and further analysis of the factors showed that Cr,Cu,Zn,As,and Pb were influenced by humans,Cd was affected by nature,Hg and W were affected by both natural and human influence.TakingChina'ssurfacewaterenvironmentalqualitystandard?GB3838-2002?as reference,fuzzy mathematics was used to establish a metal fuzzy comprehensive evaluation model for water and weight.Through calculation,we can see that Longxing river belonged to Class I surface water quality standard,Xiaomu river,Tianzhai river,Huangtian river belonged to Class II surface water quality standards,Taojiang river belonged Class III surface water quality standard,and Dajishan river belonged to Class V surface water quality standard.?3?The average contents of Cr,Cu,Zn,As,Cd,Hg,Pb,W in the middle and upper reaches of Taojiang river were 32.42,42.38,147.22,15.11,1.1,0.47,59.73,10.16 mg·kg^-1respectively.According to the Person correlation analysis,it showed that Cr,Cu,Zn,As,and Pb were significantly related to each other.After factor analysis,it was found that Cr,Cu,Zn,As,and Pb were affected more by humans.W,Cd,and Hg were affected by nature.Based on the risk assessment of average risk index method showed that Cr,Cu,Zn,As,Cd,Hg,Pb and W evaluation index ratio were 0.126?no risk?,15.808?moderate risk?and 11.601?moderate risk?,2.724?low risk?,14.248?moderate risk?and 12.577?moderate risk?,4.675?low risk?and 0.308?no risk?;according to the accumulation criterion of heavy metals Cr,Cu,Zn,As,Cd,Hg,Pb,W accumulation index values were-0.62?no pollution?,-0.21?no pollution?,-0.36?no pollution?,-1.04?no pollution?0.86?light pollution?,0.64?mild pollution?,-0.22?no pollution?,0.03?mild pollution?.According to the fuzzy cluster analysis,4,6,8,14,20,22,23,25,27,32,33,33,33,33,and 38 were heavily polluted and required targeted prevention and control.The research on eutrophication status and ecological risk of heavy metals in Taojiang River basin provides the basic data and theoretical basis for the water quality management and restoration in the basin,which is of great practical significance to ensure the drinking water safety of local residents.