填埋场内砷形态转化及归趋的微生物介导机制

The phenomenon of garbage-surrounded city aggravates the arsenic pollution in landfill, which has gained more attention greatly. Based on the phenomena that arsenic can be released into the surrounding environment from gaseous (landfill gas) and liquid (leachate) phases, and the arsenic toxicity in different redox state differ significantly, this proposed research aims to study the microbial mediated speciation and toxicity transformation of arsenic in landfill by methods including dynamic modeling landfill reactor, dominated microbe isolation, and batch landfill microcosm simulating, respectively. Firstly, the distribution of arsenic source and sink in municipal solid waste during the decomposition process will be investigated by simulating landfill reactor, and then the phenomena of microbial mediation will be evaluated. Secondly, the dominated microbes mediated the transformation of arsenic speciation will be isolated by high-throughput sequencing and computer indexing, and their metabolism on different arsenic speciation will also be figured out. Finally, the speciation and toxicity transformation of arsenic mediated by dominated microbes at different landfill stage will be elucidated. Results of this research will hopefully provide scientific proof for designated strategies of arsenic pollution control by elucidating the release mechanism of arsenic with different speciation and toxicity in landfill.

垃圾围城导致填埋场的砷污染加重，值得关注。针对填埋场的砷污染具有液相（渗滤液）和气相（填埋气）两条输出途径，而砷在不同氧化还原状态下毒性差异显著等现象，本项目以砷为目标物，填埋场为载体，依次采用动态模拟、优势微生物鉴别和填埋小生境批式模拟等手段，逐步开展填埋场内砷形态转化及毒性归趋的微生物介导机制研究。首先通过动态模拟，获得填埋场稳定化过程中砷形态的源、汇分布特征；随后通过高通量测序和计算机检索，鉴别介导砷形态转化的优势微生物并构建各微生物的砷形态代谢途径；最终通过批式模拟不同优势微生物的最适填埋生境，探讨在不同时期垃圾中各优势微生物作用下的砷形态转化及其产物的毒性归趋行为。项目的研究以揭示填埋场中不同毒性砷形态的终端输出为最终目的，为填埋场的砷污染控制策略提供针对性的依据。

：填埋场是典型的人造环境，是各种污染物的汇集地，也是不可忽视的砷污染之一。As的毒性由其形态决定特性，微生物介导As的形态转化至关重要。填埋场内微生物多样性高，且富微含生物代谢活动所需的营养物，本项目深入开展填埋场内砷形态转化及归趋的微生物介导机制研究。首先，通过大型填埋场实地采样，揭示各形态As分布特征随填埋龄改变，在填埋中期（3-5年）达峰值，填埋体内As(III)和As(V)的平均含量分别为0.91 mg/kg和5.2 mg/kg，而后逐渐趋于稳定。而且发现功能基因aioA丰度与As(Ⅲ)的氧化行为明显相关，而arrA基因和arsC基因的丰度则与As(V)的还原行为相关。其次，通过运行模拟准好氧填埋生物反应器，发现Bacteroidetes（拟杆菌）和Proteobacteria（变形菌）是优势菌群和介导As(III)解毒的主要物种。通过分析各物种在网络中的生态贡献，即各物种的Zi值（模块内连接值）和Pi值（模块间连接值），提出Pseudomonas（假单胞菌）可能是驱动As(III)解毒行为的关键物种，并从反应器内筛选分离得到5株As(III)氧化菌，分别为Pseudomonas putida、Ammoniphilus sp.wt2、Acinetobacter sp.wt3、Pseudomonas sp.yl、Microbacterium sp.ms。然后，进一步构建模拟生物反应器，研究填埋场内As(V)生物还原行为及其调控机制，在填埋场微生物的作用下，As(V)添加组（Low组和High组）与Initial组（CK）相比，As(V)还原效率明显提高，其还原效率分别为32.52%和33.07%。不同温度场下填埋场微生物的As(V)还原速率存在显著差异，还原速率为高温场（50℃）＞中高温场（35℃）＞室温场（25℃）＞低温场（10℃）。其中，低温场主导菌属为Pseudomonas，常温为Pseudomonas和Aquanacterium，中高温为Pseudomonas、Aquanacterium、Bacillus以及Clostridium，高温则为Bacillus和Clostridium。项目研究解析了填埋场As氧化还原过程及机理，从理论上完善了填埋场内As生物地球循环理论体系，为解决新填埋场维护管理、老填埋场复垦中面临的As污染治理提供了新思路。