Changes In River Water Chemistry Of Jinhua River Urban Section And Its' Controlling Factors

In order to reveal the changes in river water chemistry of Jinhua River urban section and its' controlling factors,this thesis elects rivers in Jinhua River urban section as the research object.We have observed pH,conductivity,Ca2+,Na+,K+,Mg2+,Sr2+,HCO3-,SO₄^2-,Cl-,TN and permanganate index,etc for 13 consecutive months,from August 2015 to August 2016.Combining with the local geological data,geteorological data and human activities along the river,we draw conclusions as follows:The river water of Jinhua River urban section is neutral?pH=7.33?,the EC value of the conductivity is larger,and the TDS content in the basin is lower than the global averge.The concentration of cations is in the order of Ca2+,Na+,K+,Mg2+ and Sr2+,the concentration of HCO3-in the anions is the highest,followed by SO₄^2-and Cl-.The average total anion concentration is 6.15meq/L,and the average of total cation concentration is 3.15 meq/L,which is much higher than the global average.Through the creation of anion and cation triangles,the cations in the river of Jinhua River urban section are distributed along the line Ca2+-Na++K+,and chemical composition of river water is bviously biased to Ca2+.The anions in the rivers of Jinhua River urban section are distributed along the line HCO3--SO₄^2-,and chemical composition of river water is obviously biased to HCO3-.Therefore,the chemical type of river water in Jinhua River urban section is HCO3-Ca2+.The temporal and spatial changes of water chemistry in the rivers of Jinhua River urban section are obvious.On the space side,the conductivity and TDS of the sampling points in Yiwu River section and Wujiang section are larger and the average value is higher.On the time side,the trend of water conductivity and TDS concentration in each sampling point is basically the same:the summer is higher and the winter is lower,while the river water pH is higher than the summer.The temporal and spatial changes of the main anions and cations are obvious,On the space side,the variation range and average value of cationic concentration in the sampling points of Yiwu River section and Wujiang section are higher than those of Wuyi River section?except R5 point as sewage outfall?,On the time side,Ca2+ and Na+ concentrations show significant seasonal variation characteristics in winter than in summer,the changes of K+,Mg2+,Sr2+,SO₄^2-and HCO3-concentrations are gentle and the seasonal variation is not obvious,but the changes of Cl' concentration are different from SO₄^2-and HCO3-,the variation curve fluctuates greatly and the seasonal variation is obvious.The spatial and temporal changes of the main water quality indicators are obvious,On the space side,the range and average of TN and permanganate index in the sampling points of Yiwu River section and Wujiang section are generally higher than those of Wuyi River section?except R5 point as sewage outfall?,On the time side,the changes of TN concentration in each sampling point are large and the trend is basically the same,it has the characteristics of high values in spring and autumn,low in autumn and winter,and the seasonal variation of permanganate index concentration is also obvious.The natural control factors for the chemical ion sourcing in the Jinhua River urban section is the weathering of rocks.The sampling points are basically distributed in the connection between silicate and carbonate rocks,all samples have a high Ca2+/Na+ and HCO3-/Na+ ratio,while leaning towards the silicate side.The water chemistry of the basin is controlled by silicate rocks and carbonate rocks,and is influenced greatly by silicate rocks weathering.The effect of atmospheric precipitation on the chemical composition of river water in the Jinhua River urban section is also great.At the beginning of rainfall,surface runoff carries plenty of terrigenous chemicals into the river,leading to higher TDS.The changes in chemical composition of the river water are also reduced with the increase of the precipitation in the basin,which indicates that the chemical composition of the river is.diluted by the river during the rainy season,and that the dilution of the ions by the precipitation is obvious.Based on the relationship between Cl-/Ca2+ and Cl-/SO₄^2-ratio,combined with the land use along the Jinhua River,it is found that the chemical composition of river water is mainly affected by natural factors,but with the development of urbanization,the impact of human activities is becoming obvious.Domestic sewage,livestock manure and a large number of fertilizers applied on farmland have a significant effect on the TN and permanganate index of the river,industrial drainage and unreasonable industrial activities caused by acid precipitation are the main reasons affecting the river SO₄^2-content.