真菌型阴离子表面活性剂修复多环芳烃与重金属复合污染土壤的机理研究

Some of the national soils are severely co-contaminated with organic pollutants and heavy metals, which is posing serious threats to the ecosystem and human health. Therefore, it is of significance to develop an economic, effective and green remediation technology to improve soil quality. The present anionic surfactants used for soil washing exhibit potential safety risk to the ecosystems. Also, the drivers affecting simultaneous removal of organic pollutants and heavy metals from contaminated soils using anionic surfactants remains unclear. Furthermore, the evolution of soil micro-ecological environment before and after washing are still lack of systematic studies. Herein, in this project, we will select acidic sophorolipids (ASLs) originated from nonpathogenic fungi Candida bombicola as a model washing agent and phenanthrene and Cd as representative organic and inorganic pollutants. By selecting red, yellow and black soil as typical soil types, we will use experimental and theoretical approaches to reveal, from macroscopic to microscopic scale, how the interactions between phenanthrene and Cd as well as iron oxides and other soil physicochemical properties could control the performance of ASLs. Also, we will examine the changes of the structure and functions of soil bacterial communities as well as soil enzymatic activities before and after soil washing and how the changes of soil micro-ecological properties correlate with soil physicochemical properties. The findings of this project will help us assess the ecological risk of using ASLs-based soil washing technique in different types of soil and will provide scientific guidance and technical support for the remediation of soil contaminated with complex pollutants.

我国部分土壤面临的有机－重金属复合污染问题威胁着生态安全和人体健康，因而寻求经济高效的绿色修复技术对改善土壤环境质量具有重要的意义。针对现有阴离子表面活性剂存在的潜在生态安全风险、洗脱复合污染土壤的驱动机制以及洗脱前后土壤微生态环境的演变机制仍不明确等问题，本项目拟选源于非致病真菌酵母Candida bombicola所产的生物型阴离子表面活性剂酸性槐糖脂（ASLs）为洗脱剂，以菲和镉为目标复合污染物，选取红土、黄土和黑土等我国典型土壤为研究对象，利用实验和理论计算等手段从宏观和微观尺度上剖析菲－镉的相互作用和土壤铁氧化物等土壤理化性质对ASLs同步洗脱土壤中菲和镉的调控机制，并揭示洗脱前后土壤细菌群落结构功能的演变及酶活性变化与土壤理化性质的关联机制，评估ASLs强化修复土壤的生态风险和适用土壤类型，为复合污染土壤的修复提供理论指导和技术支持。

表面活性剂强化洗脱技术（SW）是重金属和多环芳烃复合污染土壤修复的最有前景技术之一。当前SW技术往往受限于阴离子表面活性剂毒性大、洗脱复合污染土壤的驱动机制和洗脱前后土壤微生态环境变化不明确等问题而难于推广应用。针对上述问题，本项目以源于真菌酵母的生物表面活性剂槐糖脂为研究对象，研发了一套制备酸性槐糖脂（ASLs）的方法，揭示了重金属对ASLs增溶多环芳烃的影响，剖析了重金属和多环芳烃的相互作用对ASLs洗脱土壤中重金属和多环芳烃的调控机制，评估了ASLs对土壤微生态的毒性效应，构建了基于ASLs的重金属和多环芳烃复合污染土壤的修复技术。本项目的主要结果为：1.在碱解酸化的基础上，我们开发了冷冻离心的方法收集生成的ASLs，该方法可减少ASLs制备纯化过程中有机溶剂的使用；2.重金属阳离子可通过pai电子-阳离子作用，降低ASLs对多环芳烃菲增溶效果，且重金属阳离子对ASLs增溶菲的抑制作用会减弱ASLs对土壤中菲的洗脱效率，然而菲可通过pai电子-阳离子作用提高ASLs对土壤中共存重金属的洗脱效果；3.分子动力学模拟表明多环芳烃分子倾向于存在ASLs这类表面活性剂的壳层中，从而可促进胶束中增溶的菲与溶液或土壤中的重金属阳离子发生作用而离开胶束，这可能是共存重金属降低ASLs增溶和洗脱土壤中菲的潜在诱因；4.ASLs不仅可通过作为碳源促进土壤中多环芳烃降解菌的生长而提高菌株对多环芳烃的降解效果，还可通过对重金属的络合作用提升多环芳烃降解菌的耐重金属性能。本项目构建了基于ASLs的安全绿色修复技术，剖析了调控修复效率的驱动因子，项目成果将为重金属和多环芳烃复合污染土壤的修复提供理论指导和技术支撑。