soil metagenome Metagenome
Dissolved organic matter can play key roles in the biotransformation of arsenic in groundwater systems, but the effects of different external organic matter on arsenic release remains poorly understood now. In the present study, anaerobic microcosms were conducted with high arsenic aquifer sediments to investigate the arsenic biotransformation behaviors as well as microbial community response in the presence of six typical dissolved organic carbon compounds (acetate, lactate, hexadecane, AQS, fluvic acid and humic acid). The results demonstrated that arsenic release and iron reduction were significantly enhanced from the additions with acetate, lactate, AQS and humic acid compared to those amended with hexadecane and fluvic acid. During biotic incubation for 7 weeks, aqueous arsenic was firstly released and reduced into As (III), and then immobilized again, indicating the possible formation of secondary minerals. High throughput sequencing revealed that microbial communities shifted differently between labile DOM (acetate and lactate) batches and recalcitrant DOM (AQS and humic acid) batches. Labile DOM addition increased the abundance of ?? bacteria, such as Acetobacterium, Petrimonas and Fusibacter, while recalcitrant DOM sets stimulated the abundances of mainly As (V)-reducing bacteria such as Desulfomicrobium and Alkalibacter. Besides, Clostridium sensu stricto only dominated in incubations amended with lactate and HA and Proteiniclasticum, Desulfuromonas, Youngiibacter was only found in HA in a specific time,indicating that HA can enhance the growth activity of these microorganisms. Moreover, compared with other organic matter, there is a synergistic relationship between DOC concentration changes and arsenic release in HA, the reasons need to be further explored.