330 1. INTRODUCTION Acid drainage is a chronic environmental problem that arises when sulfide-rich materials oxidize in the presence of water and oxygen. This process generates acidic water loaded with sulfate and metals, whose impact can persist for decades or centuries (Nordstrom, 2011; Blowes et al., 2014). This phenomenon can be natural in origin (acid rock drainage, or ARD) or associated with mine components or materials (exposed tailings, waste dumps, deposits of unsuitable material, etc.) which, due to their granulometry and the presence of sulfides, react with environmental conditions (acid mine drainage, or AMD) after the mine is closed. In high Andean regions of Peru, which are highly vulnerable to climate extremes, the risk of AMD can be amplified by changes in precipitation and temperature patterns (Nordstrom, 2011; Blowes et al., 2014). Extreme climate variability (from prolonged dry seasons to torrential rains) can drastically alter the geochemical dynamics of these deposits. For example, it has been observed that after long dry periods followed by heavy rains, there are sudden increases in acidity and dissolved metal concentrations due to the sudden washing away of accumulated acid salts (“first flush”) (Nordstrom & Alpers, 1999; Blowes et al., 2014). Under climate change scenarios, drier summers and more intense but spaced-out rainfall intervals are expected, which could exacerbate these pulses of acid pollution. This reality raises the need to address ARD/ARD not only as a static problem, but as a dynamic one under changing climatic conditions. Although guidelines exist for AMD/AAR, the Andean region, and climate change, the explicit integration of extreme climate indices (droughts, maximum daily precipitation, duration of dry periods) into closure design and monitoring metrics is still limited; recent approaches propose quantifying these indices and mapping their uncertainty for closure decisions. Currently, the prediction and control of DAM in closure planning is often based on static and kinetic geochemical tests, along with assumptions of stationary climate. While advanced reactive transport models exist that simulate DAM generation and attenuation by incorporating variable saturated and unsaturated flow and coupled chemical reactions, the application of longterm climate projections within such models is still in its infancy. Traditional studies (Nordstrom, 2011; IPCC, 2021) have documented seasonal variations in DAM and proposed mitigation strategies based on historical conditions. However, the literature indicates that emerging climate trends (e.g., greater extremes of drought and rainfall) have not been fully integrated into acid risk assessments. For example, Nordstrom (2009) warns that remediation designs must be prepared for conditions more extreme than historical averages. Some international closure guidelines (e.g., GARD Guide) recognize the influence of climate but offer only general guidelines. In practice, scenarios such as Representative Concentration Pathways (RCPs) need to be explicitly incorporated into geochemical modeling tools for mine closure. Only recently have research approaches emerged that link climate models to acid drainage generation, highlighting a gap between climate science and environmental geochemistry applied to mine closure (Nordstrom, 2011; IPCC, 2021). Given this gap, it is critical to develop methods that integrate climate change projections into DAM prediction. The lack of such integration leads to uncertainty in the effectiveness of
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