Characteristics And Potential Ecological Risk Assessment Of Heavy Metals In Surface Sediments Of Baoxiang River, Dianchi

Dianchi is a pearl which has huge ecological function and ornamental value in Yunnan-Guizhou Plateau but it is seriously polluted in recent years.After years of governance and restoration,a series of key pollution control projects have been constructed from the source control to the end interception.During the "13th Five-Year",the Dianchi governance entered the stage of attack.Pollution control for the lake ecosystem of lake bottom sediments can not be ignored.There are many studies on the sediment of Dianchi water body at present,which focus on the geochemical analysis of elements and the assessment of heavy metal pollution,and less attention is paid to the amount of heavy metals carried in the lake sediments.In order to study the sources of heavy metals in the sediments in Dianchi,this paper takes the main rivers of Dianchi,the Baoxiang River,as the research object.From the sediment granularity and elemental geochemical characteristics,the total amount of heavy metals in the sediments,the characteristics of its occurrence form,the source of heavy metals to the evaluation of pollution,the target heavy metals(Zn,Cu,Ni,Pb and Cr)were systematically studied.Thus,the potential ecological hazards caused by the sediment of the elephant River in Dianchi are estimated,and based on this,we can infer the influence of the main lakes and rivers in Dianchi on Dianchi.The conclusions of this paper are as follows.(1)The granularity of the deposits in the Baoxiang river is concentrated in the range of clay silt,silt and sandy silt.The sediments in the river downstream of the best separation,the skewness is mainly near symmetry and the kurtosis is dominated by constant peaks.(2)The variation coefficient of the main elements in soil and sediment in the Baoxiang river is higher than that in the sediments,indicating that the soil is subjected to more the human race disturbance.In accordance with the numerical value of the weathering index,the majority of the sections are of medium chemical weathering and some areas are strongly chemically weathered.Two different weathering grades confirmed the dry and wet season climate of the humid monsoon climate zone in the northern subtropical region of Kunming.(3)The mean values of the contents of Zn,Cu,Ni,Pb and Cr in the sediments of the Baoxiang River are w(Zn)>w(Cu)>w(Cr)>w(Pb)>w(Ni).The contents and speciation of the 5 heavy metals showed apparent temporal and spatial distribution characteristics.Zn,Pb and Cr showed increasing trend with the river flow in different seasons,while Cu and Ni decreased with the flow direction of the river.The residue content of the 5 heavy metal elements decreased with the flow direction,and the extractable state content increased continuously.5 kinds of heavy metals are different degrees of influence of human activities and rivers water chemistry.(4)The potential ecological risk assessment of the heavy metals(Zn,Cu,Ni,Pb and Cr)in the surface sediments of the Bao Xiang River(Zn,Cu,Pb and Cr)was evaluated by the potential ecological risk assessment method.The potential ecological risks of the heavy metals were all slight.The pollution degree of heavy metals(Zn,Cu,Ni,Pb and Cr)in the surface sediments of the Bao elephant river is evaluated by the ratio method of secondary and primary phase distribution.It is found that Cu,Ni and Cr are not polluted,and Zn and Pb are slightly polluted in some sections of the river.(5)Most of the in BaoXiang River affected by human activities,including fertilizer and pesticide application in agriculture,sewage discharge in life,transportation pollution and so on.Some heavy metals come from clay minerals produced by rock weathering in the basin.The Baoxiang river flow and river water TSS concentration and heavy metal content of the unit value to calculate the total content of each year by the Baoxiang River sediment into Dianchi Zn,Cu,Ni,Pb and Cr were 151.14Kg/a,96.12Kg/a,37.86Kg/a,40.53Kg/a and 70Kg/a respectively.The total contents of Zn,Cu,Ni,Pb and Cr in Dianchi Lake in 90 s were estimated to be 87.14 t/a,55.42 t/a,21.83 t/a,23.36 t/a and 40.36 t/a respectively,according to the calculation formula and existing research data.