Operational zone-based assessment of metal contamination and long-term leaching predictions for active smelting site...

Smelting operations release metals into the environment, yet assessment of their dynamic contamination patterns and long-term leaching behavior at active facilities remains limited. This study examines the long-term leaching behavior of cadmium (Cd) and zinc (Zn) from contaminated soils at an active smelting site in South Korea. The investigation was conducted through a systematic analysis of 11 operational zones. A simplified model incorporating soil- and site-specific parameters was employed to predict the 30-year cumulative metal leaching mass (I_30yr, mg/m²). Total metal concentrations varied significantly across sites, and sequential extraction revealed that the metals were predominantly associated with Fe/Mn oxides and residual fractions (Cd: 65.2-95.9 %; Zn: 77.9-99.3 %). Column leaching experiments demonstrated that leaching was pH-dependent and influenced by CaO content. The model and multivariate statistical analyses revealed that leaching behavior was governed by zone-specific parameters rather than solely by the total metal content, identifying distinct leaching mechanisms: (1) infiltration-controlled zones (wastewater treatment, smelting, and sulfuric acid processing facilities) with Fe/Mn oxide-bound fractions and (2) mass-controlled zones (groundwater discharge areas and roasting operations) dominated by residual fractions. These findings provide a framework for site management strategies based on zone-specific contamination characteristics, supporting targeted remediation and contamination control efforts.