铁基材料强化硫酸盐还原菌修复重金属污染底泥的研究

Heavy metal pollution in sediment has become one of the important environmental issues, and has received a great deal of attention. As an important composition of aquatic ecosystems, sediments play an important role in affecting transformation and transfer of heavy metals in environment, and the remediation of sediments polluted by the heavy metals is crucial in the whole process of aquatic ecosystem remediation. Using microorganism and its combination techniques to restore the sediments have gradually become the research hotspot in the field of environmental science and engineering. In present study, iron-based materials were selected to enhance the biostabilization of sulfate reducing bacteria (SRB) for sediments, which included both natural and simulated sediments and contaminated by heavy metals. Firstly, the problems and its influences of remediation technology treated only by SRB were investigated, as well as the restoration mechanism of iron-based materials. On these basis, the synergic remediation mechanism of the iron-based materials enhancing SRB were mainly studied, and the growth and metabolism characteristics of SRB and its biostabilization efficiency were also both investigated, under different type of carbon source and different supply mode. Combining the studies of efficiency, stability and safety of different biostabilization technologies, the assessment method for biostabilization was established, which was used to select out an efficient, stable and safe biostabilization technology for sediment contaminated by heavy metals. The researching result is hopeful to get breakthroughs in illuminating the scientific questions and technical indicators, such as the SRB metabolic pathways and its remediation mechanisms, the synergic mechanisms of iron-based materials and the enhanced biostabilization efficiency for heavy metals. Therefore, the research has important academic significance and application prospect.

底泥重金属污染作为全球性的环境问题而备受关注。底泥是水环境的重要组成，对重金属的迁移转化至关重要，底泥修复是整个水生生态系统修复的关键。微生物及其组合技术应用于底泥修复已成为环境科学与工程领域的研究热点。本项目以模拟和天然底泥为研究对象，针对重金属污染，利用具有环境修复潜力的铁基材料来强化硫酸盐还原菌（SRB）开展修复研究。首先，通过单独修复体系，明确SRB单独修复存在的问题及影响因素、阐明典型铁基材料修复机理；在此基础上，重点研究铁基材料对SRB的强化机制，考察不同碳源不同供给方式条件下，SRB生长代谢和生物固化效果；结合修复效率、稳定性和安全性研究，建立生物修复评价方法，并利用此法优选出高效、稳定、安全的重金属生物固化修复技术。研究成果有望在阐明SRB代谢途径和修复机理、铁基材料对SRB强化机制、提高重金属生物固化效率等科学问题和技术指标方面取得突破，具有重要的学术意义和应用前景。

底泥重金属污染作为全球性的环境问题而备受关注，我国城市水体底泥中普遍存在重金属污染。底泥是水体的重要组成，重金属进入水体后会以各种形式积聚到底泥中，含量高出上覆水几个数量级，对生态环境和人体健康产生严重危害。因此，重金属污染底泥的修复引起了广泛关注，也是整个水生生态系统修复的关键。硫酸盐还原菌（SRB）可以将重金属转化为硫化物固定于底泥中，降低生物有效性，具有成本低、环境友好等优势，易于实现原位修复，具有很好的应用前景。本项目以镉为例，开展了SRB及纳米零价铁（nZVI）、有机碳、生物质炭等材料的强化对重金属污染底泥的修复以及机理研究，阐明了SRB修复过程中金属形态转化和微生物作用机制。发现在SRB修复过程中底泥中重金属的活跃态显著降低，稳定态显著增加；底泥中脱硫杆菌科和脱硫叶菌科丰度的增加，有利于稳定化合物CdS的生成，厌氧绳菌科和嗜氢菌科与SRB存在共生关系。nZVI通过为SRB提供硫酸盐还原过程中所需的电子以及提高该过程中重要酶的活性来促进SRB的生物固定，并且由nZVI本身转化生成的铁矿物，能够协同增强底泥中镉的修复效果。此外，有机碳可以使体系氧化还原电位维持在较低状态，进而促进硫酸盐的还原，而不同结构的生物质炭对SRB的修复有着不同的影响。项目结合黄瓜种子、大型水溞、方格星虫等不同类型的生物的毒性实验、底泥重金属形态分析以及薄膜梯度扩散技术（DGT）全方位开展了底泥的修复效率、稳定性和安全性研究，形成了一套系统的底泥生物修复的评价方法。在此基础上设计了易于取样的柱式反应装置，开展了SRB原位修复模拟研究，重点探究不同剖面底泥的修复效果和机制。发现当SRB在最初投放到水-沉积物界面时，界面以下约6cm的底泥能够得到很好的修复。表层底泥中的镉被固定后，足以降低镉在底栖动物中的生物有效性，同时能够抑制镉向上覆水释放的风险。研究成果可为底泥重金属污染管理、控制与修复提供重要参考，并为该技术的实际应用奠定基础，具有重要的学术意义和应用前景。