UTILIZING CU AND ZN ISOTOPES TO ELUCIDATE SOURCES AND TREATMENT MECHANISMS OF ACID MINE DRAINAGE AT THE ARGO TUNNEL WATER TREATMENT PLANT

Acid mine drainage (AMD) is a significant environmental challenge arising from the oxidation of sulfide minerals that release heavy metals into water systems. This study utilizes isotopic analyses of Cu and Zn to trace the sources of AMD processed by the Argo Tunnel Water Treatment Plant (ATWTP) in Idaho Springs, Colorado, and to evaluate the efficacy of metal dropout mechanisms within the treatment framework. By analyzing field-collected samples of influent and effluent water, as well as treatment sludge, this research maps the isotopic compositions of Cu and Zn, employing these isotopes as tracers to identify geochemical fingerprints and their specific AMD sources. The variations in δ⁶⁵Cu and δ⁶⁶Zn values offer a refined understanding of the diverse origins and intricate geochemical interactions at play. Further, this study investigates how Cu and Zn isotopes function as tracers through the ATWTP’s treatment system, highlighting opportunities to optimize the process for improved metal dropout. Although established treatment methods including neutralization and clarification are known to effectively reduce metal concentrations, this research explores the potential to enhance these processes through the targeted adsorption of metals onto Fe and Mn oxides, suggested by shifts in isotopic ratios. This examination of isotopic fractionation, especially in the context of metal adsorption, provides new avenues for boosting metal removal efficiency. Ultimately, this research not only supports the assignment of site liabilities and prioritization of remediation efforts but also enhances metal dropout efficiency, potentially supporting the recovery of critical mineral resources and reducing waste.