| With the development of urban industrialization and agricultural intensification,soil heavy metals pollution has become one of the main factors which affect soil environmental quality.In this dissertation,eight heavy metals(Cd,Hg,As,Cu,Pb,Cr,Zn and Ni)in 268 soil sampling sites of Baoying county were selected as the research object.The contents and chemical speciation of heavy metals in soils of the whole area(including five different land use types)were analyzed by using Excel,SPSS,GS+,ArcGIS software and so on.By using PI,PIN,Igeo,EF and RAC to assess the pollution level and risk level of soil heavy metals.Correlation among heavy metals in soils was researched via multivariate analysis and factorial kriging analysis.On the basis of multivariate analysis and combined with the results of pollution assessment,the potential sources of heavy metals in soils were identified.In this dissertation,from the perspective of the whole region,detailed and scientific information of the pollution level and potential sources of heavy metals in soils is to provide theoretical basis for soil remediation and soil environmental quality management.The main results were as follows:(1)The chemical speciation of heavy metals in soils of the whole area showed,the percentage of contents for Fe-Mn oxide bound states of seven heavy metals decreased in the order of Zn(14.11%)>Pb(10.58%)>Cd(9.38%)>As(9.02%)>Cu(8.46%)>Ni(8.24%)>Cr(5.06%),and the percentage of contents for their organic bound states decreased in the order of Cd(17.86%)>As(13.93%)>Zn(11.91%)>Ni(10.11%)>Cr(9.33%)>Cu(7.50%)>Pb(6.82%),and the percentage of contents for their residue states decreased in the order of Cr(82.75%)>Cu(75.98%)>Ni(73.41%)>As(70.64%)>Pb(65.31%)>Cd(62.50%)>Zn(59.26%).In soils of the different functional areas,the mean of carbonate bound states for Cd decreased in the order of industrial area>traffic area>residential area>farmland area～greenland(woodland)area,and the mean of its residue state decreased in the order of traffic area>industrial area>farmland area>residential area>greenland(woodland)area.In soils of the industrial area,the average content of the exchangeable state for Cd was greatest,which was 0.027 mg kg-1.In soils of the greenland(woodland)area,the average content of the organic bound state for Cd was greatest,which was 0.07 mg kg-1.In soils of the different functional areas,compared with other chemical speciation,the average contents(9.25～10.18 mg kg-1)of the residue state for As were larger.Compared with other functional areas,the average content of organic bound state for Cu in soils of the residential area was greatest,which was 5.84 mg kg-1.The average content of Fe-Mn oxide bound state for Pb in soils of the traffic area was greatest,for 15.24 mg kg-1,which decreased in the order of traffic area>industrial area>farmland area～residential area！greenland(woodland)area.The mean of residue state for Zn decreased in the order of greenland(woodland)area>traffic area>farmland area>industrial area>residential area.The order of the mean for five chemical speciation of Cr was similar to that of Ni.By using RAC for risk assessment,in soils of the industrial area,the sum of percentage of exchangeable states and carbonate bound states for Cd,Cu,Pb and Zn were from 10%to 30%,which showed soil environment was in the moderate risk state;however,the effect of As,Cr and Ni on soil environment was in the low risk state.In soils of the traffic area,the sum of percentage of exchangeable states and carbonate bound states for Pb and Zn were from 10%to 30%,which showed soil environment was in the moderate risk state.In soils of the farmland area and greenland(woodland)area,the sum of percentage of exchangeable states and carbonate bound states for seven heavy metals were from 1%to 10%,which showed soil environment was in the low risk state.In soils of the residential area,the sum of percentage of exchangeable states and carbonate bound states for Cu,Pb and Zn were from 10%to 30%,which showed soil environment was in the moderate risk state.(2)The standard values were taken as the reference values,PI was used to evaluate eight heavy metals in soils of the whole area,eight heavy metals were in the clean state.The result of PIN showed,the pollution level for eight heavy metals in soils of the whole area decreased in the order of Zn>Cd>Pb～Cu～Cr～As～Ni～Hg.In soils of the industrial area,Cd was heavily polluted and Zn was moderately polluted,and other six heavy metals were in the clean state.In soils of the traffic area,Zn was lightly polluted,and the PIN values of other seven heavy metals were less than one,which showed these heavy metals were in the clean or basic clean state.In soils of the farmland area,Cu and Zn were in the basic clean state,and other six heavy metals were in the clean state.In soils of the residential area,Cd,Cu and Zn were in the basic clean state,and other five heavy metals were in the clean state.In soils of the greenland(woodland)area,Cd and Zn were in the basic clean state,and other six heavy metals were in the clean state.The result of Igeo showed,the pollution level for eight heavy metals in soils of the whole area decreased in the order of Cd～Zn>Hg～As～Cu～Pb～Cr～Ni.In soils of the industrial area,Cd and Zn were moderately polluted,and other six heavy metals were in the clean state.In soils of the traffic area,Cd,Pb and Zn were in the light to moderate pollution state,and other five heavy metals were in the clean state.In soils of the farmland area,Cu and Zn were in the basic clean state,and other six heavy metals were in the clean state.In soils of the residential area,Cd,Cu and Zn were in the basic clean state,and other five heavy metals were in the clean state.In soils of greenland(woodland)area,Cd and Zn were in the basic clean state,and other six heavy metals were in the clean state.In soils of the farmland area and greenland(woodland)area,eight heavy metals were all in the clean state.In soils of the residential area,except Cu,other seven heavy metals were in the clean state.The EF values for eight heavy metals in soils of the whole area decreased in the order of Zn>Cd>Pb>Cu>As～Cr>Ni>Hg.In soils of the industrial area,Cd and Zn were moderately polluted,and in soils of the traffic area,farmland area,residential area and greenland(woodland)area,eight heavy metals were in the clean to light pollution state.The result of RI assessment showed eight heavy metals in soils of the whole area were in the light ecological risk state.The RI value of eight heavy metals in soils of different functional areas decreased in the order of industrial area>traffic area>residential area>greenland(woodland)area>farmland area.(3)Factor analysis showed,in soils of the whole area,Cd and Zn,As and Ni,Hg and Cr,Cu and Pb were positively correlated with factor one,factor two,factor three,and factor four,respectively.In soils of the industrial area,Cd-Pb-Zn,and As-Ni were positively correlated with factor one,and factor two,respectively.In soils of the traffic area,Cr,Cu,Pb and Ni,and Zn was positively correlated with factor one,factor two,factor three,and factor four,respectively.In soils of the farmland area,As and Ni,Cd and Zn,Hg and Cr,and Pb were positively correlated with factor one,factor two,factor three,and factor four,respectively.In soils of the residential area,Cd and Zn was negatively correlated with factor one and factor two,respectively;Hg,Ni,and Cu was positively correlated with factor two,factor three,and factor four,respectively.In soils of the greenland(woodland)area,As and Pb,Cr,and Zn were positively correlated with factor one,factor two,and factor three,respectively.Factorial kriging analysis showed,at nugget effect scale,there was positive correlation between Cd and Cu,Cd and Pb,Cd and Zn,respectively;there was also positive correlation between As and Cr,As and Ni,respectively.At short range scale,similar to the nugget effect scale,there was positive correlation between Cd and Cu,Cd and Pb,Cd and Zn,respectively,and there was positive correlation between Cr and Ni.At long range scale,there was positive correlation among As,Cr and Ni;there was also positive correlation between Cd and Cu,Cd and Pb,Cd and Zn,respectively.However,there was negative correlation between Cd and As,Cd and Ni,respectively;there was negative correlation between Zn and As,Zn and Ni,respectively.The positive correlation among soil heavy metals shows that they are influenced by similar factors,however,the negative correlation indicates that they are influenced by different factors.(4)In soils of the whole area,the Cd and Zn contents were possibly affected by natural factor and human activities,and the Cu and Pb contents were also possibly affected by human activities,however,the As,Ni,Cr and Hg contents were primarily affected by natural factor(e.g.soil parent material).In soils of the industrial area,the Cd and Zn contents were possibly affected by point pollution sources(e.g.industrial wastewater discharge),the Cr,As,Ni,Hg,Pb and Cu contents were primarily affected by natural factor.In soils of the traffic area,the Cd,Hg,Cu,As and Cr contents were primarily affected by natural factor,the Cu,Pb and Zn contents were possibly affected by human activities(e.g.vehicle exhaust emission).In soils of residential area,the Cu contents were possibly affected by human activities(e.g.heavy metals waste),the contents of other seven heavy metals were primarily affected by natural factor.In soils of the farmland area and greenland(woodland)area,the contents of eight heavy metals were primarily affected by natural factor. |
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