纳米零价铁联合白腐菌强化修复湿地沉积物重金属污染的行为机制及生态毒性效应研究

Heavy metal contamination is serious in sediment of Dongting Lake wetland. Microbial remediation based on white rot fungi is an important method for in situ remediation of heavy metal contaminated wetlands, but its performance is limited by the remediation time and efficiency in practical applications. The combination of nanoscale zero-valent (nZVI) and microorganism is an effective way to remediate heavy metal contamination, but the mechanism of using nZVI and white rot fungus to remediate the heavy metal contaminated wetland sediment is not clear. So, the Pb and Cd-contaminated wetland in the East Dongting Lake was studied, and a combined system of nZVI and white rot fungus was proposed, and its remediation process was optimized. The morphological transformation characteristics of heavy metals in wetland were studied, and various analytical techniques such as X ray diffraction were applied to reveal the behavior mechanism of the combined system in enhancing the remediation of heavy metal contamination. Finally, the project will comprehensively analyze the ecological toxicity of the combined system from the aspects of the release potential of heavy metals, soil enzyme activity response and microbial community response, to reveal its environmental effects in remediation of heavy metal contaminated wetlands. The project is expected to provide theoretical basis and practical reference for remediation of heavy metal contaminated wetlands, improve the ecological environment of wetland and promote the development of the theory and key technologies in remediation of heavy metal contamination.

洞庭湖湿地沉积物中重金属污染严重。基于白腐菌的微生物修复技术是原位修复重金属污染湿地的重要方法，但其性能受修复时间和修复效率的制约。纳米零价铁与微生物联用是实现重金属污染高效修复的有效途径，但利用纳米零价铁与白腐菌联合体系修复重金属污染湿地沉积物的有关机理尚不清楚。本项目以东洞庭湖沉积物重金属铅镉污染为研究对象，拟构建修饰型纳米零价铁与白腐菌联合修复体系。首先优化调控联合体系构成及应用过程；然后研究修复过程中重金属的形态转化特性，并结合X射线衍射等现代分析技术，探讨联合体系强化修复重金属污染的行为机制；最后从重金属的解吸释放潜力、土壤酶活性响应、微生物群落响应等多方面全面解析联合体系的生态毒性效应，以揭示其对重金属污染湿地的环境效应。该项目有望为重金属污染湿地修复提供理论依据和实践参考，改善湿地生态环境，推动重金属污染修复理论与关键技术的发展。

本项目针对湿地沉积物重金属污染问题，构建了基于纳米零价铁与白腐菌的重金属污染联合修复体系。首先开展了纳米零价铁与白腐菌联合修复体系的优化构建研究，分析明确了环境因子对联合体系修复性能的影响规律；其次研究了联合体系对湿地沉积物重金属污染的修复性能及其强化修复作用机理，最后从修复前后重金属的浸出毒性、土壤酶活性和微生物群落结构及多样性等方面，阐明了联合体系修复重金属污染湿地的环境生态风险。主要研究结果为：（1）白腐菌和纳米零价铁对重金属的去除有协同作用，白腐菌/纳米零价铁联合体系对重金属的去除过程符合准二级动力学，且在偏中性条件下的修复效果较好，有效降低了铁溶出所造成的二次污染问题；（2）白腐菌/纳米零价铁联合体系对重金属的主要去除机制为白腐菌对重金属的胞外络合吸附，添加纳米零价铁能促进白腐菌对重金属的胞外络合吸附作用，白腐菌胞外聚合物(EPS)能与铁发生内层配位形成P-O-Fe键，加速富含羟基官能团的纤铁矿、磁铁矿等铁矿物形成，从而促进对重金属的去除；（3）经白腐菌/纳米零价铁联合体系修复后，湿地沉积物中重金属的TCLP态重金属含量显著下降，重金属浸出毒性有效降低，残渣态重金属含量显著提高，即重金属得到了有效稳定化处理。此外结合酶活性测定结果及16S rRNA测序分析发现，nZVI/白腐菌联合修复体系能使湿地沉积物过氧化氢酶、脱氢酶、酸性磷酸酶和脲酶等均保持较高的活性，对微生物群落结构的影响较小，能使微生物物种保持一定丰度和多样性。