THE EFFECTS OF ORGANIC-ACIDS ON THE LEACHING OF HEAVY-METALS FROM MINE TAILINGS

A laboratory study was conducted to determine whether the concentration of heavy metals, zinc (Zn), lead (Pb), and cadmium (Cd), in leachate from mine tailings could be affected by the presence of organic acids exuded by plant roots and microbes in the rhizosphere. Geochemical modeling predicted that some organic ligands found in the rhizosphere have the capability to complex and increase the solubility of Zn. These results were confirmed by batch and column studies in which mine tailings were exposed to 0-10000 mu M organic acids. The leachate was analyzed for Zn, Pb, and Cd content and for organic acid concentration.