Physicochemical characteristics and microbial community analysis of a wetland system treating acid mine drainage

The elevated heavy metal concentrations and acidic pH conditions characteristic of Acid Mine Drainage (AMD) pose significant environmental challenges, necessitating the development of effective remediation strategies. This study systematically evaluated the performance of a surface-flow constructed wetland system in Ma'anshan, China, for AMD treatment through comprehensive physicochemical characterization and microbial community analysis. The multi-stage wetland system, comprising four interconnected units vegetated with Phragmites australis, Typha angustifolia, and Arundo donax, was monitored for water quality parameters, sediment characteristics, and microbial diversity. Results demonstrated significant improvements in water quality, with pH increasing from 5.18 to 7.41 and substantial removal efficiencies observed for heavy metals: complete (100.00%) removal of Fe, 92.00% removal of Zn, 61.80% removal of Mn, and 63.60% removal of chemical oxygen demand (COD). Sequential extraction analysis revealed that residual fractions constituted the predominant form of sediment-bound heavy metals (65.70%-70.20% for Fe). Proteobacteria make up 58% of the microbial community. Sulfuricurvum combines denitrification and sulfide oxidation, while SRB like Desulfuromonas convert sulfate to sulfide. Nitrospinae oxidizes ammonia to nitrate, Thaumarchaeota oxidizes ammonia to nitrite, and Parkl vularcula facilitates denitrification. In order to maintain cycles and support wetland function and AMD treatment, hydrolytic bacteria break down organic materials. These findings establish the effectiveness of constructed wetlands (CWS) in AMD remediation through synergistic phytoremediation and microbial metabolic processes, offering an ecologically sustainable approach for the restoration of mining-impacted areas.