Investigation of mineralogical and bacteria diversity in Nanxi River affected by acid mine drainage from the closed coal mine: Implications for characterizing natural attenuation process.

Abstract

Due to the supply-side reform and environmental protection in China, many small coal mines have been closed since 2015. However, acid mine drainage from these coal mines are continuously discharging into many rural creeks, which requires the systematical investigation on the variations of geochemical and environmental biological aspects in these water systems. In this study, from a classic acid mine drainage (AMD) from a closed coal mine of Hunan, China, various sediments and water samples in different sections were collected and analyzed. According to the corresponding Mineralogical and simple bacterial characteristics analysis (16S rRNA gene sequencing), the main findings were: 1) Secondary iron-containing minerals gradually transited from Gr(CO32-) (green rust), Sh (schwertmannite) to Akg (Akaganeite) and more stable Gt (Goethite); 2) compared to the pristine sediment, these minerals decreased the acid-neutralizing capacity and cation exchange capacity (CEC) of sediments; 3) Proteobacteria and Firmicutes were the dominant phyla and the obvious variation of Firmicutes species was observed in the creek affected by AMD, which probably could been a biological index to diagnose the natural attenuation of AMD. These results could be greatly significant to understand typical variations of creek attenuation and bacterial community in the presence of high metal and sulfate concentration.