A study was conducted on abandoned Cu mill tailings ponds rich in chalcopyrite, to assess the heavy-metal concentration, using four extractants (HOAc, EDTA, DTPA, and CaCl2), and the concentrations were compared with the control soil. Of the seven metals studied, the concentrations of total Cu and Ni in tailings, sediments and control soil were found to exceed toxicity limits. Total and EDTA-extractable Pb were found to be highest in the control soil as compared to tailings and sediment. Of nine naturally colonizing species in the abandoned Cu tailings ponds, four could be termed ‘Cu hyperaccumulators’, i.e. Ammania baccifera (1478–2931 mg kg–1 dw), Eleocharis geniculata (1122–1493 mg kg–1 dw), Fuirena ciliaris (486–1348 mg kg–1 dw) and Typha latifolia (554–1247 mg kg–1 dw). These plants also accumulated Ni at concentrations greater than 100 mg kg–1 in their roots without showing any symptoms of injury. Plants naturally colonizing Cu tailings showed metal concentrations in roots ten to 50 times greater than in shoots, indicating that these plants have developed inherent physiological mechanisms for storage of metals in root tissues. The bioconcentration factor for Cu in roots of Ammania baccifera was found to be >1, and for other species between 0.5 and 0.8, hence these could be used for bioremediation of abandoned Cu mill tailings sites rich in Fe, Cu, Ni, and Zn. The bioconcentration factor for Zn in the root and shoot portions of all the vegetation was found to be higher than for other metals (0.3 to 21).

Key words: Cu-tailings, heavy metals, hyperaccumulator, natural vegetation

Land Contamination & Reclamation, 16 (2), 135-153