Rising atmospheric carbon dioxide ignites metal mobilization in acid mine drainage

Rising atmospheric carbon dioxide is projected to exceed 800 ppm by 2100, yet its impact on acid mine drainage (AMD), which is currently contaminating 480,000 km of rivers, remains unclear. Here we combine a global meta-analysis of 82 AMD-associated sites covering diverse climate zones and ore types with laboratory experiments across environmentally relevant carbon dioxide gradients. We find that atmospheric carbon dioxide is the dominant global predictor of the key acid-forming genus Acidithiobacillus. Elevated carbon dioxide enhances microbial carbon fixation and electron transport, accelerates ferrous iron oxidation, intensifies acidification, and subsequently increases cadmium and zinc mobilization by 0.56%–1.93% for each 100 ppm rise in atmospheric carbon dioxide. Scenario-based climate projections further suggest a 0.25%–10.60% increase in cadmium flux from AMD by 2100. These findings suggest that rising atmospheric carbon dioxide should be considered in global AMD risk assessments and mine-waste remediation planning. Rising atmospheric carbon dioxide upregulates Calvin cycle and accelerates ferrous iron oxidation, intensifying acidification and mobilization of cadmium and zinc in acid mine drainage by 0.6-2% per 100 ppm increase in carbon dioxide, based on controlled experiments paired with global meta-analysis.