Distribution Characteristics,Sources And Ecological Risk Assessment Of Heavy Metals In Soils Of Qinghai-Tibet Plateau

To reveal the distribution of heavy metals in the surface soil central and eastern Qinghai-Tibetan Plateau,twelve heavy metals were analyzed using multivariate analysis,and the soil quality was assessed by ecological risk assessment.Major results are as follows:In this study,Ba concentration range from 301.70 to 647.65 mg·kg-1,the maximum value was 438.82 mg·kg-1;Cd concentration range from.0.05 to 0.72 mg·kg-1,the maximum value was 0.17 mg·kg-1;Co concentration range from 3.68 to 21.65 mg·kg-1,the maximum value was 11.35 mg·kg-1;Cr concentration range from 26.30 to 272.72 mg·kg-1,the maximum value was 71.43 mg·kg-1;Cu concentration range from 7.50 to 60.58 mg·kg-1,the maximum value was 23.88 mg·kg-1;Mn concentration range from 274.97 to 1119.98 mg·kg-1,the maximum value was 640.95 mg·kg-1;Mo concentration range from 0.33 to 2.37 mg·kg-1,the maximum value was 0.78 mg·kg-1;Ni concentration range from 9.17 to 162.80 mg·kg-1,the maximum value was 31.63 mg·kg-1;Pb concentration range from 9.43 to 122.51 mg·kg-1,the maximum value was 29.08 mg·kg-1;Sb concentration range from 0.09 to 35.68 mg-kg-1,the maximum value was 1.89 mg·kg-1;Sc concentration range from 2.90 to 16.42 mg·kg-1,the maximum value was 9.53 mg·kg-1;Zn concentration range from 24.98 to 136.56 mg·kg-1,the maximum value was 73.60 mg·kg-1?There were significant positive correlations among the heavy metals.Take acvantage of Principal Component analysis to judge the sources,the twelve heavy metals could be divided into four factors.Factor 1,Co,Cu,Mn,Ni,Sc,Zn,Al and Fe,mainly represented natural sources.Factor 2,Ba,Cd,Mo,Pb and Zn,were influenced by both traffic and natural sources.Factor 3,Cr,Ca and Mg,were mainly controlled by natural sources.Factor 4,Pb,mainly represented traffic sources.The result of accumulation index method showed:six types of soils were polluted by Cd,among them,the II,III,IV,VI and X were in the mild pollution,the VII was in the middle pollution;V were under the condition of mild pollution by Ni and Sb;The other nine heavy metals,Ba,Co,Cr,Cu,Mn,Mo,Pb and Sc were non-pollution in all kinds of soils.The result showed that partial sampling sites had been polluted by Cd,Ni and Sb.The potential ecological risk index showed that,Cd was at medium ecological risk in the average of eitht single heavy metal pollution factor from 73 samplings,the others were at slight ecological risk.In the seven types of soils,Cd showed strong hazard in ? and ?,showed middle ecological risk in II,IV,VI and X,and showed mild ecological risk in ?.The comprehensive potential ecological risk index showed that the soil of Qinghai Tibet Plateau in the overall state of the minor and the harm of heavy metals,Cd contributed the largest potential ecological risk index(RI index)value,followed by Cr,Ni and Pb.