Property evolution and driving factors of electrolytic manganese residue (EMR) during long-term natural weathering

Electrolytic manganese residue (EMR), a waste by-product of manganese production, poses significant ecological risks. Natural succession remediation provides a sustainable strategy for risk control; however, the long-term evolution of EMR properties and the microbial drivers remain poorly understood. In this study, we investigated dynamic changes in physicochemical properties, aggregate structure, and enzyme activities in an EMR storage yard in Hunan Province over 0, 1, 3, 5, and 10 years of natural weathering. EMR was acidic, primarily composed of quartz and gypsum, and exhibited high salinity and heavy metal concentrations, with Mn (1397–43,139 mg/kg), Ni (100.9–254.5 mg/kg), Cu (70.7–116.6 mg/kg), Pb (52.1–129.9 mg/kg), Zn (242.3–445.6 mg/kg), and Cr (107.4–255.8 mg/kg), dominated by Mn pollution. Over 10 years, the heavy metal pollution index decreased by 94.9 %, aggregate stability improved via the formation of coarse aggregates, and activities of nitrogen (LAP, NAG) and phosphorus (ACP) hydrolases increased by 6.99-, 6.14-, and 27.58-fold, respectively. The integrated biological risk (IBR) index decreased by 22.3 %, and EMR properties gradually approached those of natural soil. Microbial community succession was dominated by Proteobacteria, Actinobacteriota, and Ascomycota, which adapted to heavy metal stress through cooperative interactions and Y-strategy growth. IMCC26256 and Morchella were identified as key taxa, strongly correlated with soil properties and enzyme activities, playing pivotal roles in EMR ecological remediation. This study provides a theoretical basis for managing ecological risks and guiding industrial crop cultivation near heavy-metal waste storage sites. • The property evolution of EMR in 10 years was analyzed comprehensively. • EMR showed ecological remediation, and environmental risks were reduced. • Bacteria adapt to heavy metal stress through rapid growth (Y-strategy) and cooperative symbiosis. • IMCC26256 and Morchella were key species driving the evolution of EMR.