Chemosphere, Vol. 29, No. 8, pp. 1691-1699, 1994 Pergamon Elsevier Science Ltd 0045-6535(94)00344-0 Printed in Great Britain 0045-6535/94 $7.00+0.00 EFFECTS OF PLANTS AND SOIL MICROFLORA ON LEACHING OF ZINC FROM MINE TAILINGS M.K. Banks I, A.P. Schwab .2, G.R. Fleming 1, and B.A. Hetrick a ~Department of Civil Engineering 2Department of Agronomy 3Department of Plant Pathology Kansas State University Manhattan, KS 66506 (Received in Germany 18 March 1994; accepted 19 August 1994) ABSTRACT A greenhouse study was conducted to determine whether the concentration of zinc (Zn) in leachate from contaminated soil could be affected by plant, mycorrhizal fungi, or soil bacterial interactions. Zinc uptake by plant roots and Zn concentrations in roots and shoots were lower in plants inoculated with mycorrhizal fungi. The mass of Zn in the leachate was greatest from pots in which plants were grown in the absence of microbial amendments. Although the presence of plants alone increased the average concentration of Zn in the leachates, the presence of soil microbes eliminated this effect. Infection of plant roots with mycorrhizae did not reduce Zn leaching relative to that with plants alone. Results from this study indicate that revegetation of mining waste sites may increase the leaching of Zn, especially when soil microflora have not been fully restored. INTRODUCTION In southeast Kansas, mining sites were active for more than 100 years (1850-1970). Abandoned mine tailings, common in this area, are high in heavy metals and have contributed to increased levels of Zn, lead (Pb), and cadmium (Cd) in the groundwater and surface runoff (Spruill, 1987). Increased incidents of chronic liver and kidney cancer, heart disease, skin cancer, and anemia have been attributed to metal pollution by mine tailings (Neuberger et al., 1990). Little vegetation occurs on many of these contaminated mining sites in southeast Kansas. Within the mine tailings area, only isolated patches of grasses exist. Besser and Rabeni (1987) suggested that vegetative cover could reduce runoff and erosion from these mine tailings. However, cover materials and vegetation may release complexing agents that could increase the mobilization of toxic metals in the leachate, thereby increasing the risk of contamination of groundwater. Prasad et al. (1976) observed that chelating agents significantly increased the diffusion of Zn in alkaline soil. Plant roots may directly influence water transport and metal movement in contaminated soil by providing channels of flow that bypass normal soil retention processes. Soil microorganisms can contribute significantly to revegetation of disturbed sites by developing a stable soil structure, releasing required nutrients through mineralization, and producing growth regulating substances * Corresponding author 1691