Environmental monitoring of La Concordia mine (Salta province, Argentina): assessing heavy metal bioaccumulation and physiological responses of Parastrephia quadrangularis.

The Puna region is distinguished by its extreme environmental conditions and highly valuable mining resources. However, the unregulated management of mine tailings poses a significant threat to the ecological integrity of this region. This study assesses the environmental impacts of mine tailings at La Concordia mine (Salta province, Argentina) and examines the physiological and biochemical adaptations of Parastrephia quadrangularis (Meyen) Cabrera that enable its survival under this extreme conditions. Our findings reveal that prolonged weathering of mine tailings results in the generation of acid mine drainage characterized by low pH levels (< 3.5) and elevated concentrations of As, Fe, Cu, Pb, and Zn. These levels exceed drinking water standards by 5-10 times for As, 6-13 times for Zn, 80-120 times for Pb, 20-380 times for Fe, and 4-10 times for Cu. Soil analyses highlight low pH, high salinity, and elevated concentrations of Zn (310 mg kg), Pb (153 mg kg), and Cu (128 mg kg). Despite these harsh environmental conditions, 7 plant species where identified, with Parastrephia quadrangularis being the only species present at the most polluted site. This species exhibits high heavy metal bioaccumulation and robust tolerance mechanisms against heavy metal-induced oxidative damage, as evidenced by stable total chlorophylls and malondialdehyde content, and increased levels of carotenoids, proline, and phenolic compounds. These findings emphasize Parastrephia quadrangularis as a promising candidate for revegetation and phytostabilization for sustainable mine closure programs in La Puna region.