Growth response, uptake and mobilization of metals in native plant species on tailings at a Chilean copper mine

Chile has many mine tailing deposits available for phytoremediation through the establishment of metal-tolerant plants. To guide such efforts, it is necessary to know whether roots exclude or take up metals, or if metals are mobilized to shoots. We evaluated a polyculture of ten native species 6 years after they were planted directly into tailings, amended with mycorrhiza before planting or planted with compost. All species were assessed for survival and hare damage. Growth, vigor, chlorophyll content index, and chlorophyll fluorescence were measured in seven species, and root and shoot concentrations of 11 metals and As were measured in five. All species had some level of stress, but there was no clear pattern related to foliar metal concentrations or amendments, the latter also having little effect on growth or survival. Copper, Fe, and Mo concentrations exceeded threshold toxicity levels for leaves and for animal feed in several species. Copper was most concentrated in the roots, and readily mobilized to leaves in three of the five species tested, but not in Prosopis chilensis (algarrobo) and Quillaja saponaria (quillay). Because of lower uptake overall, quillay is recommended for stabilizing tailings while also reducing transport to aerial tissues.