Response of bacterial communities and function to dissolved organic matters in groundwater contaminated by landfill leachate.

The migration and transformation of dissolved organic matter (DOM) caused by landfill leachate leakage affected the phylogenetic development of bacterial communities in groundwater around the landfill. Previous studies mainly focused on the hydrochemical properties of DOM in groundwater contaminated by landfill leachate and the relationships between groundwater quality parameters and bacterial communities. However, the changes in DOM components and bacterial communities caused by landfill leachate leakage and their correlations remained unclear. In this work, we analyzed the evolution characteristics of DOM and identified the bacterial communities and their corresponding functions in groundwater around the landfill. The results showed that DOM content in groundwater increased after the diffusion of landfill leachate to groundwater. Significant differences in characteristics between DOM components were presented at different locations in the landfill leachate plume due to the physical dilution and bacterial degradation of DOM. One of the obvious manifestations was the tendency of humic acid-like substances to accumulate at downstream points. Samples from the contaminated aquifer had higher diversity and abundance of bacterial communities than those in the uncontaminated aquifer. Anaerobic or facultative anaerobic bacteria played predominant roles in contaminated groundwater, due to the input of organic matter, nitrate, and ammonia nitrogen. Redundancy analysis indicated that the content of fulvic acid-like DOM had a conspicuous impact on the composition of bacterial communities in the polluted groundwater. Vogesella were the dominant bacteria at the genus level in groundwater around the landfill. Furthermore, Vogesella were significant for microbial utilization and played an important role in the production of fulvic acid-like DOM. These results indicated that landfill leachate pollution posed a potential threat to the structure and function of bacterial communities in groundwater, and provided a basis for exploring the interaction between DOM composition and bacterial communities in groundwater plume contaminated by landfill leachate.