The Distribution Patterns And Environmental Constraints Of Active Microbial Community In High Arsenic Groundwater From The Hetao Basin,Inner Mongolia

High arsenic groundwater has negatively impacted on the healthy of local residents in the Hetao Basin,Inner Mongolia,which is one of the most important social issues.This stuy is aiming at investigating the diversity and community structure of the active and inactive bacteria of groundwaters and the sediments of Hetao Basin by comprehensively using hydrogeochemical and molecular biological methods(high throughput sequencing and quantitative real-time PCR),determining factors control the microbial diversity and community structure,quantifying arsenic-related functional genes,and evaluating the relationship among arsenic-related functional genes,environmental factors,and active microbes.The main findings in this stuy are shown as follows.1)The sulfate reducing bacteria and iron reducing bacteria are dominant species in groundwater of the plain.Groundwater in the piedmont is predominated by sulfate reducing bacteria.Groundwater Fe(II),As,TOC and SO42-/Cl-influence the distribution of the active microbial community.The machanisams of groundwater arsenic enrichment in the piedmont are different from the plain.2)Groundwater total As,SO42-/Cl-,ORP and NH4-N and As and iron manganese oxides in the sediments affect the community distribution of the active microorganism in sediments.3)Although the active microbial community structures of groundwater or sediment are similar to those of groundwater or sediment nearby,the active microbial community structures of groundwater are different from those of depth-match sediment.Active sulfate reducing bacteria and the arsenic reduction bacteria in sediments show positive correlations with groundwater total As and Cl-/SO42-.Bacteria in sediments are influenced by the microbial community of the depth-match groundwater.4)The gene expression of arrA in groundwater has a positive correlation with groundwater total As,TOC and P.But the arrA expression of sediments has a negative correlation to arsenic content of sediments.High groundwater arsenic and the reducing environment enhance the activity of the arrA encoding bacteira,which increases the transcription and translation of the arrA,and leads to a positive relationship between groundwater arrA and arsenic.Sediment arsenic decreases as the arrA increases since more arsenic was released into groundwater in the presence of overwelming arrA.5)Positive correlations are observed between the aioA expression of groundwater and groundwater parameters,including H2 S,Mn and NO3-.In addition,the aioA expressionis positively correlated the active bacteria,including Desulfocapsa,Rhodospirillaceae_unclassified and Ralstonia in groundwater.In sediments,positive correlation existed between the aioA and Cupriavidus.6)The expression of arsB in groundwater increases along the groundwater flow path,which is well correlated with the consumption of groundwater SO42-.The relative abundance of active Paludibacter has a positive correlation with arsB expression.