Risk Assessment And Numerical Simulation Of Heavy Metal Pollution In Drainage Ditch Of Shapotou District,Zhongwei City

The ecological environment in the upper reaches of the Yellow River is very important,and its pollution status and ecological health risk research and evaluation have always been the focus of academic circles.The Shapotou District of Zhongwei City is located in the central and western part of the Ningxia Hui Autonomous Region.It is located in the upper reaches of the Yellow River.Its drainage ditch is discharged into the Yellow River,which has a negative impact on the water quality of the Yellow River.In this study,in March,June and October of 2017,the heavy metal elements such as Cr,Cu,Cd,Hg and As in four drainage ditch waters in Zhongwei City were sampled and analyzed,and the spatial and temporal distribution characteristics of major heavy metals in the drainage ditch were analyzed.Principal component analysis was used.And factor analysis method to screen heavy metals in the four drainage ditch of Zhongwei City,which have great influence on water environment;combined with MIKE11 hydrodynamic-water quality coupling model,simulate the transport process of heavy metal rivers in the drainage ditch of Shapotou District,Zhongwei City,and study the distribution of heavy metals The research results of characteristics and laws can provide basis or basic data for water environment pollution eontrol in Shapotou District of Zhongwei City.The main results of this study are as follows:(1)The drainage ditch in Shapotou District of Zhongwei City is seriously polluted and basically belongs to the inferior V water quality standard.The four metals of Cr,Cu,Cd and Hg are affected by both rainfall and temperature.The seasonal variation is basically higher in summer than in spring and winter.The seasonal variation of As is basically higher in spring and winter than in summer.The concentration of heavy metals in the drainage ditch with contaminant points and multiple drainage channels is slightly higher.(2)Based on principal component analysis,the heavy metal factors in different periods are divided into several principal components,which basically reflect the water quality information of the drainage ditch,and analyze the correlation of heavy metals in each period.The water environment factor in March 2017 can be divided into three main components,and the cumulative variance contribution rate is 80.00%.The water environment factor in June 2017 can be divided into four principal components,and the cumulative variance contribution rate is 92.07%;The water environment factor can be divided into three main components,and the cumulative variance contribution rate is 90.84%.During the study period,the water quality information of the main components in each period can be basically reflected.Based on the factor analysis,the most important water environment heavy metal factors in each period of the drainage ditch were analyzed In March 2017,the main factors affecting the heavy metals in the drainage ditch environment of Shapotou District of Zhongwei City were Cd,Cr,Hg,Cu and As.The main influencing factors were Cr,Cd and Hg.In June,Shapotou District of Zhongwei City was affected.The main factors of heavy metals in the drainage water environment are As,Cu,Hg,Cd and Cr.The main influencing factors are As,Cu,Hg and Cd.The main factors affecting the heavy metals in the drainage ditch environment in Shapotou District of Zhongwei City are in turn.For Cd,Cu,Hg,Cr,As,the main influence factors are Hg,Cu,Cd.Combined with the results of research and analysis,Cd and Hg are the main heavy metals affecting the water quality of the drainage ditch in Shapotou District,Zhongwei City.(3)Using the Nemero comprehensive pollution index method to evaluate the heavy metal pollution in the drainage channel of Shapotou District,Zhongwei,the single factor pollution index of Cr and Hg is higher than other heavy metals,and the pollution degree is large in June,and the pollution degree in March and October is higher,small.In March,the whole basin was moderately polluted.The pollution of heavy metals was Cr>As>Cu>Cd>Hg,and As,Cd,Hg and Cu were all heavy metals without pollution.In June,the whole basin was a strong pollution,and the eomprehensive pollution risk was abnormally high.The pollution of heavy metals was Hg>Cr>Cu>Cd>As.As,Cd and Cu were all heavy metals without pollution,and Hg had the largest single factor pollution index.At 8.8,it is a strong pollution.The fifth and sixth drainage ditch in October belonged to non-polluting.The eighth and ninth drainage ditch were low_pollution.The Pollution of heavy metals was Cr>Hg>As>Cu>Cd,Cr,As,Cd,Hg and Cu.It belongs to heavy metals without pollution.(4)Select the measured values of heavy metal pollutant monitoring indicators in March,June and October 2017 to determine the parameters of the model,and take the sampling point of sampling point 19(drainage into the Yellow River)as the target From the comparison of the simulated values of the pollution factors with the measured values,it can be seen that the overall range of the simulation error is 0.13%?16.7%,and the error is within the acceptable range,indicating that the simulation effect is good and the model construction is reasonable.It is concluded feat the hydrodynamic condition and water quality movement of the drainage ditch in Shapotou District of Zhongwei City can be obtained through the MIKE11 hydrodynamic-water quality coupling model,and the concentration and distribution of heavy metal ions can be predicted,which is the water environment of Zhongwei City drainage ditch.The basic data and theoretical basis for integrated govermance,conservation and sustainable use.