Hydrochemical characteristics and microbial community evolution of Pinglu river affected by regional abandoned coal mine drainage, Guizhou province, China

Acid mine drainage (AMD) from abandoned coal mines has become the main source of recharge for Pinglu River. The revelation of the hydrochemical characteristics of regional AMD contamination and the evolution of river microbial communities can contribute to the source management and ecological remediation of AMD pollution. In this study, we collected twelve abandoned coal mine drainage (group M), eight polluted river water samples (group R) and five river sediment samples for comprehensive analysis. Results indicated that SO 4 -Ca·Mg was the main hydrochemical type of group M samples, and the Ca/Mg ratio of drainage was significantly negatively correlated with SO 4 2- (R 2 =0.612, p <0.05). The confluence of AMD resulted in a gradual change of river hydrochemical type from SO 4 ·HCO 3 -Ca·Mg to SO 4 -Ca·Mg, accompanied by a simultaneous decrease in sediment microbial community diversity. In addition, significant differences in microbial community composition and diversity were observed between the upstream and downstream sediment of Pinglu river, and these differences were mainly attributed to pH, TOC and TP. Results of BugBase phenotype prediction demonstrated that the relative abundance of anaerobic microorganisms in river sediment gradually decreased from upstream to downstream (from 24.77 to 12.46%), which was mainly contributed by genera such as Geobacter, Citrifermentans, Luteitalea and Vicinamibacter .