Effect of sludge amino acid–modified magnetic coal gasification slag on plant growth, metal availability, and soil enzyme activity

Eroded mine soils are a serious environmental problem in many parts of the world. Coal gasification slag, a byproduct of the coal gasification process, was modified with sludge-derived amino acids for the purpose of remediating eroded mine soils. Amino acid–modified magnetic coal gasification slag (AMS) was evaluated for its ability to decrease heavy metal erosion, improve soil aggregate structure and plant growth, and enhance microbial enzymatic activity. Alhagi sparsifolia (A. sparsifolia) was grown in greenhouse experiments under different AMS concentrations (0%, 1%, 5%, and 10%). The growth rate of A. sparsifolia increased with increasing AMS concentrations, and the optimal portion of AMS in soil was 7.5%. A. sparsifolia grown in mine soil amended with 7.5% AMS significantly (p < 0.05) decreased bioavailability of all heavy metals studied in this work (except for iron [Fe]) and increased (p < 0.05) activity of three soil enzymes: phosphatase (PA), urease (UA), and β-glucosidase (β-GA). In addition, the reusability of AMS was very good. AMS-amended mine soil may interact with growing plants to cycle needed nutrients while immobilizing toxic metals. AMS is thus a promising amendment for remediating eroded mine soils.