Likelihood of using phytoremediation for mine-tailing management in Chile.

Chile has more than 750 mine tailings across the country, mainly distributed in the northern region, which also includes a biodiversity hotspot and the driest desert in the world. So far, tailing management has included chemical and physical stabilization of tailings, exclusively. This research examined the perceived likelihood of stakeholders, namely: Academia, Industry, environmental Non-Governmental Organizations, and Government officials, in the management of tailings and explored their attitudes toward the inclusion of plants and their associated microbes, as an additional stabilization technology, through an online questionnaire (n = 43). We aimed to answer What was the perceived likelihood of stakeholders for using phytoremediation for mine-tailing management in Chile? The consensus opinion across sectors is that there is general lack of proper tailings management in Chile. There is a critical willingness to incorporate phytoremediation, with a preference for using native plants. An absence of demonstrably successful phytoremediation projects, funding and access to suitable plants are perceived to be significant limitations. Local community involvement is considered key to successful restoration of tailings.

The novelty of this research work comes from finding consensus opinion across sectors about the lack of proper management of tailings in Chile and a critical willingness to incorporate phytoremediation as an additional stabilization technology. Furthermore, it provides insights from professional stakeholders on the need for more studies on native plants that can be used in phytoremediation, to diversify the representation of stakeholders, and to include input from local communities, directly affected by mines.

Enlightening the Pathway of Phytoremediation: Ecophysiology and X-ray Fluorescence Visualization of Two Chilean Hardwoods Exposed to Excess Copper.

In the present climate emergency due to global warming, we are urged to move away from fossil fuels and pursue a speedy conversion to renewable energy systems. Consequently, copper (Cu) will remain in high demand because it is a highly efficient conductor used in clean energy systems to generate power from solar, hydro, thermal and wind energy across the world. Chile is the global leader in copper production, but this position has resulted in Chile having several hundred tailing deposits. We grew two Chilean native hardwood species, quillay (Quillaja saponaria Molina) and espino (Vachellia caven (Molina) Seigler & Ebinger, under three increasing Cu levels (0, 50, and 100 µM) for 6 months in a greenhouse setting. We measured growth, photosynthetic performance and elemental contents of leaves and roots to further evaluate their potential for phytoremediation. Growth of quillay was unaffected by Cu treatment but growth of espino was enhanced, as was its photosynthetic performance, indicating that espino may have an unusually high requirement for copper. Excess Cu was mostly restricted to the roots of both species, where X-ray fluorescence (XRF) mapping indicated some tendency for Cu to accumulate in tissues outside the periderm. Calcium oxalate crystals were prominently visible in XRF images of both species. Nickel (but not Cu) showed a concurrent distribution pattern with these crystals.

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.