Distribution characteristics and environmental significance of sulfate-reducing bacterial community in high arsenic groundwater from different depth of Hetao Plain, China

Abstract:

[Objective] To investigate the relative abundance, community composition and diversity of sulfate-reducing bacteria in high arsenic groundwater of different depths, and to reveal the main geochemical factors (e.g., δ³⁴S-SO₄^2–) affecting the distribution characteristics of sulfate-reducing bacterial community in high arsenic groundwater and the environmental significance. [Methods] High arsenic groundwater samples from both shallow and deep aquifers were collected from Hetao Plain, a typical high arsenic groundwater-distributed area in China. Various geochemical parameters were measured and the relative abundance of 16S rRNA gene and dsrB gene of the samples was quantified by qPCR. High-throughput sequencing of dsrB gene was conducted to reveal the community composition of sulfate-reducing bacteria. Statistical analysis was further performed to analyze the correlations between geochemical variables and sulfate-reducing bacterial community characteristics. [Results] The relative abundance of dsrB gene in shallow samples was higher than that in deep samples. In shallow high arsenic groundwater, the relative abundance of dsrB gene and the δ³⁴S-SO₄^2– were both significantly positively correlated with the concentration of CH₄. In contrast, the relative abundance of dsrB gene showed positive correlations with the concentrations of SO₄^2– and DOC in deep high arsenic groundwater. The high-throughput sequencing of dsrB gene displayed that the α-diversity of sulfate-reducing bacteria in deep groundwater was remarkably higher than that in shallow groundwater. Sulfate-reducing bacteria in the study area were divided into 264 operational taxonomic units (OTUs), including ten predominant orders such as Desulfobacterales, Nitrospirales, Rhodospirillales and Syntrophobacterales. The relative abundance of each order and the environmental factors affecting their abundance were different in shallow or deep groundwater. Specifically, the relative abundance of Nitrospirales in shallow groundwater was positively correlated with the concentrations of As_T and δ³⁴S-SO₄^2–, indicating the key role of Nitrospirales in arsenic migration and transformation in shallow groundwater. The redundancy analysis (RDA) found that As_T, CH₄ and Fe²⁺ were the key environmental factors controlling the distribution of sulfate-reducing bacterial community in groundwater of the study area. [Conclusion] The relative abundance, community composition and diversity of sulfate-reducing bacteria in deep and shallow high arsenic groundwater varied, and were affected by geochemical parameters.