Organic matter

Ecology

Bacteria

Biology

Geotechnical engineering

Canonical correspondence analysis

Geology

Soil water

Paleontology

Soil pH

Organic chemistry

Hydrology (agriculture)

Environmental chemistry

Environmental science

Abundance (ecology)

Microbial population biology

Soil science

Acid mine drainage

Chemistry

Soil test

The Science of The Total Environment

Acid mine drainage (AMD) poses a potential environmental risk due to the low pH combined with high concentrations of toxic metals and sulfate. The Hengshi River in China is continually contaminated by the AMD from upstream mining areas and this river was selected as a study site to investigate the spatial distribution of Cu, Cd, Pb, Zn and the microbial communities in the paddy soil in vicinity of the river. Various geochemical parameters were determined for five sites, where river water was sampled together with paddy soil (at three depths) and soil pore water. The distribution of toxic metals at these sites was ranked as soil > river water > pore water. The metals in the soil samples were divided into five extractable fractions. With the increase of soil depth, F1Zn, F2Pb, F3Zn, F4Zn, F5Cu basically produced a decreasing trend. The sum of the F1 and the F2 fractions of the toxic metals followed the order of Cd > Pb > Cu > Zn. Among the predominant bacteria detected were Fe- and S- metabolizing genera, including Anaeromyxobacter, Thiobacillus, and Geobacter. Based upon canonical correspondence analysis, sand content, Cu and pH correlated most strongly with the composition of the microbial communities. Significant correlations were found between toxic metal fraction and environmental parameters such as organic matter and total S content, while Fe only had a minor effect. The toxic metal fractions were the dominant drivers in changing the soil microbial community. The potential ecological risk of the toxic metals was assessed as Cd > Cu > Pb > Zn. Collectively, these results suggest that the geochemical gradients caused by AMD altered the toxic metals speciation and enriched relevant soil microbiota which adapted to the different conditions.

Spatial distribution characteristics of the microbial community and multi-phase distribution of toxic metals in the geochemical gradients caused by acid mine drainage, South China