Designing Multi-Layered Waste-Derived Technosols for Long-Term In-Situ Passive Treatment of Acid Mine Drainage

Abstract: Acid Mine Drainage (ARD/AMD) remains one of the most severe environmental liabilities in the mining sector, characterized by extreme acidity (𝑝𝐻 < 3) and toxic heavy metal loads. Active chemical neutralization is economically unsustainable post-mine closure. This review synthesizes recent advances in constructing multi-layered, waste-derived Technosols—engineered soils constructed from industrial and municipal byproducts—designed for long- term, passive, in-situ treatment of AMD. We evaluate the synergistic mechanisms of combining alkaline wastes (e.g., steel slag, fly ash, bauxite residue) with organic wastes (e.g., spent mushroom compost, anaerobic digestate) to promote concurrent chemical neutralization, sorption, and biological sulfate reduction. This paper outlines the structural layering dynamics, biogeochemical pathways, and critical engineering bottlenecks governing system longevity, hydraulic conductivity, and substrate passivation.