甲基β环糊精强化土壤PAHs反硝化厌氧降解及微生物群落响应机制

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed in soils. Pollution with persistent PAHs has threatened soil ecological safety and human health and has been becoming a big environmental problem. Therefore, remediation of PAH-contaminated soil has become one crucial issue which needs to be solved. Enhanced microbial degradation is considered as one of environmental and cost effective technologies for the remediation of PAH-contaminated soils. Compared with the widely studied PAHs biodegradation under aerobic conditions, much less attention has been paid to the anaerobic biodegradation of PAHs. Furthermore, the lack of oxygen under anaerobic condition makes PAHs degradation extremely difficult and critical biochemical processes during anaerobic degradation process, including specific reduction system, provision of alternate electron acceptors, changes of PAHs bioaccessibility and the relationship among different microbial functioning communities, remain largely unknown. Therefore, anaerobic microcosm study will be set, combining Response Surface Methodology, a first-three-compartment conceptual model, the stable isotope probing, and the high throughout sequencing technologies to systematically investigate the role of methyl-β-cyclodextrin in the enhanced anaerobic biodegradation of PAHs in soils under nitrate reducing condition. From the perspective of soil microbiology and soil chemistry, the PAHs degradation dynamics, the rate-limiting factors, and the response mechanism of different microbial functioning communities will be clarified during the bioremediation. This study will provide important theoretical direction and scientific evidence for the application of the enhanced anaerobic bioremediation technology of PAHs in soils.

多环芳烃（PAHs）是土壤中广泛存在的有机污染物，其“三致”效应会危及土壤生态安全与人体健康，是亟需解决的土壤环境问题。微生物强化降解是一种环境友好、经济高效的土壤修复技术。国内外学者对好氧条件下微生物降解土壤PAHs已开展了较为系统的科研工作，而厌氧条件下微生物降解土壤PAHs的过程则有待深入研究，包括：还原反应的特定体系、PAHs微生物可利用性的变化、电子受体的供给情况及厌氧微生物群落的响应过程等。本项目拟在纯厌氧环境中，向污染土壤添加不同浓度的PAHs微生物可利用性促进剂（甲基β环糊精）和电子受体（硝态氮），运用定量化的数学模型、13C-PAHs稳定性同位素探针和高通量测序等方法，从土壤化学和微生物学角度，揭示甲基β环糊精强化土壤PAHs反硝化厌氧降解机制，阐释影响厌氧降解进程的关键限制因素，探明体系内厌氧微生物群落的响应过程，为研究土壤PAHs厌氧降解修复提供理论指导和科学依据。

多环芳烃（PAHs）是土壤中广泛存在的有机污染物，其“三致”效应会危及土壤生态安全与人体健康，是亟需解决的土壤环境问题。微生物强化降解是一种环境友好、经济高效的土壤修复技术.本实验在厌氧条件下，向污染土壤添加不同浓度的PAHs微生物可利用性促进剂甲基β环糊精和电子受体硝酸根，运用三阶段解吸概念模型和高通量测序等技术手段，发现：.1.在厌氧条件下开展反硝化作用对土壤PAHs消减的影响，发现同时添加1%（w/w）MCD和硝态氮对于总量PAHs最大去除量约为57%。.2.通过Tenax TA树脂提取修复前，土壤中自由解吸的PAHs，并运用污染物三阶段解析模型拟合其解吸过程，发现添加1% w/w MCD处理较CK处理可显著提高总量PAHs的解吸量（p<0.01），同时也显著提高土壤中快速解吸组分PAHs的比例及解吸速率。.3.通过分析Tenax TA提取不同环数PAHs在土壤培养前后的比例变化，在CK和M处理中，由于PAHs自由解吸量大于微生物去除量，所以微生物因子是限制修复进程的主要原因；在N和MN处理中，厌氧土著菌群不仅降解了PAHs可自由解吸的含量，还多降解了相应含量，说明解吸因子是决定整体修复进程的关键因素。.4.单独或同时添加MCD或硝态氮处理对土壤细菌和真菌的多样性有显著影响，土壤反硝化细菌、硝酸还原酶活性、土壤反硝化基因nirS、nirK、cnorB、qnorB、nosZ基因丰度在N处理和MN处理中得到显著强化（p<0.05），为协同深度厌氧降解土壤中PAHs提供了可能。高通量测序结合传统分离手段发现变形菌门（Proteobacteria）的赖氨酸芽孢杆菌属（Lysinibaciilus）细菌中普遍检测出反硝化功能基因，说明反硝化功能细菌在土壤厌氧降解过程中发挥了潜在的积极作用。.本项目通过在室内厌氧条件下开展微域实验，运用数学模型及高通量测序等手段 ，从土壤化学和微生物学的角度揭示MCD强化土壤PAHs反硝化厌氧降解的动力学特征，阐述了制约厌氧降解进程的关键限制因素，探明了体系内厌氧微生物群落的响应过程，为研究土壤中PAHs厌氧降解修复提供了理论指导和科学依据。