Geochemical Characteristics Of Heavy Metals In Suspended Matter Of Lakes In Yunnan Plateau

The heavy metals in suspended latter of typical plateau lakes in Yunnan prvoice are reserched The work help us understand the current situation and the trend of heavy metal pollution in plateau lakes.The samples of Dianchi Lake,Yangzonghai Lake,Fuxian Lake and Qilu Lake are collected in 2018.The concentrations of heavy mclal elements Ni,Cu,Zn,Mo,Sb,Pb,Th,U etc.in the lakes are analyzed using a Inductive Coupled Plasma Mass Spectrometer.Health risk assessments of heavy metal in these Lakes are also performed by heavy metal health rish(HMHR)model.The pollution status and possible sources of heavy metals in suspended matters in the lakes are discussed by using multivariate statistical method that provide useful scientific reference for the prevention and control of water pollution in plateau lakes in Yunnan Province.(1)The concentrations of Cr,Ni,Cu9 Zn,Cd and Pb in the four lakes are lower than the risk control stanards for contamination of China.The higher values of Mn in Dianchi Lake are founded in DL5 and DL2,the distribution of Mn in Dianchi Lake area varies greatly;the maximum values of Cr are founded in DL5,the distribution varies greatly;the larger values of Al are founded at DL5,DL2 and DL1;the larger values of Ni are founded in DL1,DL2 and DL5;the larger values of Zn are founded in DL1,DL2 and DL5.The order of concentrations of heavy metals iin Dianchi Lake area are:Al>Cr>Mn>Zn>Ni>Cu>Pb>Mo>Co>Sb>Cd>Th>U>Ag.The concentrations of heavy metals in Fuxian Lake areas are:Al>Cu>Mn>Cr>Zn>Ni>Pb>Sb>Cd>Ag>Th>U.The highest value of Mn in Qilu Lake are founded at QL7,and the distribution of Mn in Qilu Lake area varies distinctly;the highest value of Cr are founded in QL7 and QL2,which distributes equality in the whole lake;the larger values of A1 are founed in QL1,QL6 and QL8,which distributes equality in the whole lake;the larger value of Ni are founded in QL2,QL3 and QL4;the larger concentration of Zn are founded in QL4 and QL7;the concentration of Cu is lower than that of the risk control stanards for contamination of China.The coefficient of variation(CV)is 0.27,which distributes equality in the whole lake.The average concentrations of Cd is 0.22ug/g,which is higher than the natural background value at all sampling fomis.The order of concentrations of heavy metals in Qilu Lake are Al>Ni>Mn>Cd>Cr>Zn>Ag>Cu>Sb>Pb>U>Thi The order of concentrations of heavy metals in Yangzonghai Lake are Al>Cr>Zn>Mn>Ni>Cu>Pb>Sb>Ag>Cd>Th>U.(2)The heavy metals Al,Pb,Th,Sb,Cu and Ni in suspended matter of four lakes are mainly existed in residual fomis.In Dianchi Lake,the proportion of A1 in DL5,DL6 and DL9 residual fomi is higher;the proportion of Pb in DL3,DL7 and DM 1 residual forn is higher;except DL3 and DL8 the proportion oIf residual form in other sampling sites are more than 90%;the proportion of Sb residual forl in DL1 and DIL8 arc higher.The main forms of Cr and Cd are iron-manganese oxide bound forms.In addition to DL1 and DL10,the proportion of iron-nanganese oxide bound fomis is more than 93%in Cr,and the proportion of Cd in DL7 and DL9 is higher,which has strong potential hazards.Ag mainly exists in organic bound fomi.Mn mainly exists in AEC form,and the proportion at DL2,DL5 and DL11 are higher.The main forms of Sb and Th in Qilu Lake are residual form,which accounts for a high proportion of QL1,QL5 and QL8 at sampling sites.Although Zn accounts for a high proportion of residual form,the proportion of AEC is 33.7%,so Zn has strong ecological hazard;Cr and A1 are mainly organic-bound,in QL2,QL3 and QL5 account for a high proportion.The main forms of Mn are AEC.Except QL7 and QL8,the proportion of Mn is more than 90%.The proportion of Cd,Cu,Pb and U unstable forms is more than 70%.The main forms of Zn,Cu,Pb5 Th and Sb in Fuxian Lake are residue form,while the main forms of Mn are AEC form and iron-ianganese oxide bound form.Al and Cr mainly exist in organic bound form,while Cd and Ni distribute equality,the proportion of unstable form is very high proportion,which has great potential ecological hazards and should be paid altenlion.The nain forms oIf Zn,Cu,l)b,Th and Sb in Yangzonghai are residual form.Al,Ni and Ag mainly exist in organic bound form,Mn mainly exist in AEC form,and Cr mainly exist in iron-manganese oxide bound form,which has strong potential hazards.The speciation distributions of Cd and U are similar.Both of them are mainly unstable,accounts for 82.54%and 82.03%respectively.Although the total amount of Cd and U are relatively small,the proportion of unstable forms is relatively high,so they have strong potential hazards.(3)The health risk assessment model recommended by the US Environmental Protection Agency(USEPA)and the classification system compiled by various international agencies are used to evaluate the health risk of heavy metals in four lakes.Among the chemical carcinogens,the annual personal risk of DL1,DL2 and DL5 at the sampling sites in Dianchi Lake area are higherthan the maximum acceptable risk of 1×10-4 stipulated by the U.S Environmental Protection Agency(USEPA).The annual personal risk of Cd in QL4 and QL8 samples in Qilu Lake area are 5.20×10-5a-1 and 5.32×10-5a-1,which are higher than the maximum acceptable risk level recommended by the International Committee on Radiation Protection(ICRP)of 5.0×10-5a-1.The individual annual risk of all non-carcinogens in water samples such as Cu,Pb,Mn and Zn are much lower than the maximum acceptable risk level proposed by countries and structures.The risk of human health hazards caused by heavy metal pollution in four Lakes mainly comes fron chemical carcinogens,while the risk of human health of non-carcinogens can be neglected.(4)The sources of heavy metals:A1 in Dianchi Lake area,the larger values of the concentrations are observed in DL1,DL2 and DL5,which mainly include the West and South coasts of Dianchi Lake.The sources of pollution can be classified as agricultural pollution.The larger concentrations of Cr occur in DL6,DL7 and DL8 in Caohai and northwest of Dianchi Lake.The sources of pollution are classified as industrial pollution.The concentrations of Cu,Pb;Zn are higher at DL1 and DL2 sampling sites.The source of pollution are mainly domestic sewage discharge.The higher concentrations of Al in Qilu Lake are founded at QL1 and QL8 in the northeast of Qilu Lake.The source of pollution are agricultural pollution.The higher concentions of Mn are mainly founded in QL7,located in Yangguang Town in the middle and eastern of Qilu Lake.The main source of Mn is natural sources.Sb,Cu and Cr are higher at QL2,QL3,QL4 and QL5.The pollution sources are urban living pollution sources.Heavy metals in the central part of Fuxian Lake are mainly from natural sources.Domestic waste water and industrial waste water are the main causes of heavy metal pollution.In addition,there are a large number of tourist villages in northwest side of Fuxian Lake.The pollutants such as domestic sewage,garbage and livestock manure flow directly into the lake along with rainwater.There is no obvious pollution in east area.The main metal source of suspended matter in Yangzonghai Lake is authropegenic.The main pollution sources(industry)of heavy metals in Yangzonghai Lake areas are mainly distributed in the west,north and south of Yangzonghai Lake areas.