Phytostabilization of trace elements and C isotope composition of Atriplex atacamensis Phil. cultivated in mine tailings treated with organic amendments.

Mining generates large quantities of mineral processing wastes that are typically stored in mine tailings (MT) ponds. Long-term exposure of the surrounding areas to the material from the tailings ponds has been reported to have adverse effects on both human health and the environment. The purpose of this study was to evaluate the ability of Atriplex atacamensis Phil. to phytostabilize metals (Cu, Fe, Mn, and Zn) and sulfur (S) when grown directly on mine tailings with and without compost (C) and humic substance (HS). The stress status of A. atacamensis Phil. was also evaluated through the C isotopic composition of bulk leaves. A 120-day greenhouse experiment was conducted and three treatments were evaluated: (i) MT without any amendments (control), (ii) MT + C (dose: 89 ton ha), and (iii) MT + HS (0.72 ton ha). Mine tailings material exhibited low salinity, alkaline pH, high extractable S-SO concentrations, and low fertility; total Fe, Mn, and Zn concentrations were within the reference range for mine tailings, but total Cu concentrations were high at 1860 ± 236 mg kg. The HS had higher pH, EC, CEC, and available concentrations of N, P, and K than compost, while S-SO concentrations were similar in both amendments. C NMR analysis showed that the HS contained more alkyl, aromatic, and phenolic groups, while the compost was dominated by O-alkyl and carboxyl groups. At the end of the experiment, the MT + C treatment achieved a significant decrease in Cu, Fe, and Mn concentrations in the roots and aboveground parts of A. atacamensis Phil. and an increase in Zn values in both tissues. Both amendments increased the sulfur content in the aboveground parts, while metal concentrations under the HS treatment proved similar to control. Furthermore, the δCV-PDB values obtained in this study indicate that the organic amendments did not cause additional physiological stress to the plants compared to the MT treatment. Overall, A. atacamensis Phil. was shown to have the ability to phytostabilize metals and sulfur, making it a potential candidate species for in situ evaluation of the phytostabilization process on mine tailings.