Fractional distribution and risk assessment of heavy metal contaminated soil in vicinity of a lead/zinc mine

The pollution characteristics of Pb, Cd, Zn, Cu and Ni in soil of lead−zinc mining area were studied. The results indicate that the contamination degree followed the sequence of Cd>Pb>Zn>Ni>Cu and concentrations of Pb, Cd and Zn exceeded corresponding limits of the Chinese National Soil Environmental Quality Standard III. The soil was extremely polluted by Cd (Iego=5.26), moderately to heavily polluted by Zn (Iego=2.38), heavily to extremely polluted by Pb (Iego=4.13). The results of BCR three-step sequential extraction procedure show that the active Cd, Pb and Zn were relatively high and might exert adverse effects on the plants grown in the soil, while Cu and Ni existed in soil with a relatively stable form. Potential ecological risk results indicate that soils were engaging in a high potential ecological risk by pollution of Cd and should be given rise to concern.