植物根际菌群对河道底泥中高分子量PAHs共代谢降解机理研究

River sediment contamination by polycyclic aromatic hydrocarbons (PAHs) is a severe environmental problem in China, and the effective control and remediation of the high-molecular-weight polycyclic aromatic hydrocarbons (H-PAHs) in river sediments are both important and difficult. This study explores the H-PAHs biodegradation in river sediments. The co-metabolism of H-PAHs by rhizosphere bacteria of emergent plants was studied under natural conditions, focusing on the metabolic pathways, the spatial and temporal distribution of metabolic products, and the metabolic dynamics. Furthermore, two artificial technologies are proposed for enhancing remediation of the H-PAHs contaminated river sediments based on the above results, namely dosing additional carbon sources and dosing immobilized high efficient bacteria around the plant rhizosphere. The effect of several critical factors on the productivity and activity of the key enzymes in the H-PAHs biodegradation are systematically investigated, including the optimization of additional carbon source components, the competitive inhibition between additional carbon sources and H-PAHs, and the validity analysis of different immobilization methods and dosage methods. Then the mechanism and operation strategy of the proposed artificial technologies for H-PAHs co-metabolism enhancement are revealed. The present study would benefit the understanding of the H-PAHs co-metabolism by rhizosphere bacteria, and provide a theoretical direction for the remediation of H-PAHs contaminations in river sediments.

我国河道底泥普遍存在PAHs污染问题，其中高分子量多环芳烃（H-PAHs）污染是河道底泥污染控制及修复的难点。本项目以河道底泥中H-PAHs作为目标污染物，研究在自然条件下，挺水植物根际菌群对H-PAHs的共代谢降解机理，重点分析H-PAHs的代谢途径、降解产物的时空分布和动力学趋势；在此基础上，提出外加共代谢碳源和在植物根际周边投加固定化高效降解菌两种人工强化技术，围绕提高关键酶合成和活性，探讨碳源优化配比、碳源与H-PAHs之间的竞争性抑制机制、高效降解菌的固定及投加方式与强化效应之间的关系，阐明两种技术对根际菌群共代谢降解H-PAHs的强化作用机理。通过本项目研究，形成完善的植物根际菌群共代谢降解H-PAHs理论体系，为河道底泥中H-PAHs污染修复提供理论指导。

高分子量多环芳烃（H-PAHs）因其具有更强的毒性和难降解性，是河道底泥中多环芳烃（PAHs）污染治理的重点和难点。本文选择了H-PAHs中检出频率和丰度都很高的荧蒽作为H-PAHs的代表物，研究了植物-微生物联合修复的方式对底泥中荧蒽污染的去除机理。.试验通过植物筛选，最终选择菖蒲作为河道底泥污染的修复植物，通过对菖蒲根际菌群的筛选获取两株对荧蒽降解效率最高的菌株，经鉴定分别为Rhodococcus aetherivorans strain IcdP1（简称红球菌IcdP1）和Penicillium purpurogenum strain DTQ-HK1（简称青霉素菌DTQ-HK1）。选择葡萄糖、麦芽糖、菖蒲根系分泌物、HA和蒽-菲混合物分别作为外加碳源，研究外加碳源对荧蒽降解的影响。发现当C葡萄糖:C荧蒽=1:1时外加碳源对红球菌IcdP1降解荧蒽的强化效果最明显，当C麦芽糖:C荧蒽=3:5时外加碳源对青霉素菌DTQ-HK1强化降解荧蒽的效果最好，且葡萄糖与麦芽糖强化降解机理主要是通过促进荧蒽溶出及促进菌株生长实现的。虽然投加外加碳源前后菌株对荧蒽的降解过程均遵循一级动力学，但降解速率明显不同。在上述碳源投加比例下，经42d培养，红球菌IcdP1对荧蒽降解率达到76.30%，与未加碳源的降解率相比提高了38.84%；青霉素菌DTQ-HK1对荧蒽降解率达到81.75%，与未加碳源的降解率相比提高了29.53%。采用分时段投加碳源方式较一次性投加方式能够进一步提高降解菌对荧蒽的降解效率。GC-MS分析发现，以荧蒽作为唯一碳源时降解菌对荧蒽的分解并不彻底，产物多为含苯环、杂环和长链化合物，投加外加碳源后荧蒽的降解更为彻底，尤其是青霉素菌DTQ-HK1在外加麦芽糖碳源后，降解荧蒽的产物多以短链小分子物质为主。.通过对荧蒽降解菌DTQ-HK1固定化载体的筛选，确定10目粒径的玉米芯最适合作为微生物固定化载体。微生物经玉米芯固定化能够增强微生物对环境条件变化的抗冲击能力，特别是重金属的影响。与悬浮菌液相比，外加碳源条件下固定化微生物能够明显提高“菖蒲-降解菌-外加碳源”联合降解体系对底泥中荧蒽的降解效率，历时75天就可以使底泥中荧蒽的去除达到100%，降解速率较相同体系下悬浮菌提高了31.8%。