Copper Uptake by Adesmia atacamensis in a Mine Tailing in an Arid Environment

Abstract

This work evaluates the potential of Adesmia atacamensis, an endemic species from the North of Chile, in phytoremediation processes of copper mining tailings. The selection of this species was based on the fact that its presence was found in 4 copper mining companies that are close to each other, its endemic quality, and its great capacity to adapt to the adverse climatic conditions of the sector of the project, characterized by having a semi-arid climate. In the experiment, the concentrations of 5 metals of environmental connotation for the country’s mining were measured: Cu, Fe, Cd, Pb, and Zn; however, given the small concentrations in Cd, these could not be measured by the team. The applied experimental design quantified the variation of bioconcentration and translocation factors (BCF and TF) for the following treatments: (1) tailing control without amendment (T0), (2) tailing plus 4% CaCO3 + 3% vermicompost (VC), and (3) tailing + 8% CaCO3 + 6% VC. In addition, for treatments T1 and T2 (T0 was not considered as it is the control treatment), the following levels of mycorrhiza were considered: 0, 10, 15, and 20 g m−2. The Baker and Brooks criteria and the BCF were used to evaluate the species as hyperaccumulators. Regarding the first criterion, high concentrations of copper were found in the shoots (shoots) of the specimens, which generally exceeded 1000 mg kg−1, with an average of 1513 mg kg−1, which allowed classifying the species as a copper hyperaccumulator; however, when compared with the BCF criterion, given that all the values were less than 1, they indicated that the species was an excluder of all the evaluated metals. Given the high concentrations of metals in the tailings, in this work, the plant has been considered as a hyperaccumulator of copper. Another indicator was the TF, which, for all experiments, resulted in a value greater than 1 for Fe, Pb, and Zn, which shows that A atacamensis translocates effectively these metals from the roots toward the aerial part and, therefore, presents the potential to accumulate metals in the aerial part. Regarding the treatments carried out, no significant impact was detected.