| Abstrakt: |
Heavy metals are potentially toxic to human life and the environment. Metal toxicity depends on chemical associations in soils. For this reason, determining the chemical form of a metal in soils is important to evaluate its mobility and bioavailability. Sequential extractionwas used to fractionate four heavy metals (Cd, Cu, Ni, and Zn) from nine contaminated soils into six operationally defined groups: water soluble, exchangeable, carbonate, Fe-Mn oxide, organic, and residual.The residual fraction was the most abundant pool for all four metalsexamined. A significant amount (2.4--44 percent) of Zn was present in the potentially available fraction: nonresidual fraction. A major portion (40--74 percent) of Cu was associated with the organic, FeMn oxide, and carbonate fractions in most of the soils. Contamination of Cd and Ni in these soils was not as severe as Zn and Cu. Assuming that mobility and bioavailabilitv of these metals are related to their solubility and geochemical forms, and that they decrease in the order of extraction sequence, the apparent mobility and potential bioavailability for these four metals in the soils were: Zn greater than Cu greater than Cd greater than Ni. Metal distributions in different chemical fractions in these soils depended on respective total metal concentrations, except for Zn. [ABSTRACT FROM AUTHOR] |
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