Geochemical Characteristics And Pollution Assessment Of Heavy Metals In Cultivated Land Of Aga Town,Liupanshui,Guizhou Province

Due to the rapid development of urbanization and economy in China,various heavy metals enter the soil in different forms due to industrial,mining and human activities,soil contamination has become a hot issue in the field of food chain accumulation in the human body.Liupanshui is a typical mining city in Guizhou Province,and mineral exploitation has brought prominent soil pollution problems.This dissertation takes the surface soil of cultivated land in Aga Town of Liupanshui City as the research object,investigates the pollution status of heavy metals in cultivated land soil,sets 425 sampling points,totally 425 samples,respectively,to determine and analyze the pH value and the contents of arsenic,cadmium,chromium,copper,mercury,nickel,lead and zinc.The sources and distribution characteristics of heavy metals in soil were analyzed by correlation analysis,cluster analysis and principal component analysis.Pollution degree and potential ecological risk of heavy metal in farmland soil were evaluated by single factor pollution index method,Nemerow comprehensive index method,ground accumulation index method and potential ecological hazard evaluation method.The following conclusions and understanding were drawn from the above studies:1.The results of heavy metal content determination showed that the contents of As,Cd,Cr,Cu,Hg,Ni,Pb and Zn were higher than the soil background values of Guizhou Province except that Pb was smaller.Only Cd,Cu and Ni in cultivated land were higher than the national soil environmental standard limits,and the other four elements were lower than the national soil environmental standard limits.As,Cd,Cr,Hg,Pb and Zn may be related to local traffic pollution and the extensive use of pesticides;Cu and Ni may come from weathering products of parent rocks.2.The results of heavy metal and As element pollution assessment,the pollution degree of As,Cr,Hg,Pb and Zn elements in single factor pollution index method are near the warning line.Ni is slightly polluted.Cd and Cuyou are heavily polluted.The pollution degree of As,Cr,Hg,Pb and Zn in the method of grinding accumulation index is not obvious,while that of Ni is slightly to moderately polluted,and that of Cd and Cu is moderately polluted.In Nemerow's comprehensive pollution index method,the location of general pollution accounts for about 6%,that of obvious pollution accounts for about 13%,and that of serious pollution accounts for about 81%.Generally speaking,the conclusion of a single factor pollution index method is consistent with that of ground accumulation index method.3.The results of potential ecological hazard assessment show that the potential ecological risk of Cd is strong from the point of view of the potential ecological risk of single heavy metal element.The potential ecological risks of As,Cr,Cu,Hg,Ni,Pb and Zn are slight ecological hazards.According to the potential ecological risk of various heavy metal,the potential ecological risk of the whole region is moderate ecological hazard.Among them,slight ecological hazards account for 67%,moderate ecological hazards account for 10%,strong ecological hazards account for 15%and strong ecological hazards account for 8%.According to the contribution rate of ecological hazards,Cd contributed the most,accounting for 74.9%,while Pb and Zn contributed the least,accounting for about 0.3%.The single contribution index of heavy metal in cultivated soil is Cd>Hg>Cu>Ni>As>Cr>Pb=Zn.