Evaluation of Acid Mine Drainage Sludge As Soil Substitute For The Reclamation of Mine Solid Wastes

Abstract

The reclamation of mine waste deposits is imperative but often hindered by the scarcity of natural topsoil. Studies have used various materials to reconstruct topsoil but mainly in coal mines, with scant information for metalliferous mines. Acid mine drainage sludge (AMDS), as a mass-produced waste in metalliferous mines, is a potential topsoil substitute because of its capacity to buffer acidification and support plant growth. In this study, a pot experiment with three plant species was conducted to evaluate the environmental safety and sustainable fertility of AMDS with the amelioration of fertilizers. Results showed that all the plants could survive in the AMDS even without fertilizers. The contents of heavy metal(loid)s were high but remained stable over the experimental period. Improving the AMDS with fertilizers enhanced its nutrient supply by increasing macronutrient contents and activities of soil enzymes, leading to significant increases in plant biomass. The AMDS also sustained its nutrient status throughout the experiment. Nevertheless, the extremely low NH4+-N and bioavailable phosphorus contents made these nutrients hardly accessible to plants, owing to the composting of the organic manure and the low richness and diversity of the bacterial community in the AMDS. Present results suggest that AMDS can be used as a viable and safe substitute for natural soil in reclaiming mine solid wastes but also needs proper improvement, especially for enhancing the microbial richness and diversity.