多环芳烃与重金属复合污染土壤的固定化微生物同步修复机制

Ecological security and human health have been threatened by PAH-metal co-contamination in soil. Therefore, to seek an economic, effective and green bioremediation technology has a good theoretical and practical significance. Based on the low activity of inoculant bacteria in soil during bioaugmentation and still unclear mechanism on remediation of co-contamination soil, in this project, pyrene and Cd in soil will be studied and pyrene-degrading bacteria will be immobilized in the core-shell ORMOSIL gel for efficient removal of PAHs and simultaneous stabilization of heavy metal in co-contaminated soil. The silica shell will adsorb pyrene and Cd, meanwhile, bacteria growth and proliferation by using pyrene will occur in the core. Interactions among the immobilized bacteria, pyrene/Cd and soil are the leading clue. Details are listed as follows: (1) investigating the characteristics, vitality and performances of this immobilized bacteria; and on this basis, (2) systematically studying interactions and interface microstructural characteristics of the immobilized matrix, bacteria and pyrene/Cd, then verifying influences of the matrix and pyrene/Cd on bacteria; (3) exploring the distribution and transfer features of pyrene/Cd and bacteria between soil particles and the immobilization matrix, then further revealing the synchronization mechanism of PAHs degradation and heavy metal stabilization in co-contaminated soil by immobilized bacteria in core-shell silica gel, based on the comprehensive analysis. The finding of this project will provide a new thought and scientific support to exploit green and effective bioactive materials for bioremediation of co-contamination site.

多环芳烃-重金属复合污染土壤威胁着生态安全和人体健康，因而寻求经济、有效和绿色的修复技术具有重要的理论和现实意义。针对微生物强化修复中注入菌在土壤中的活性较低和复合污染土壤修复机制仍不明确等问题，本项目拟以土壤中芘和镉为目标污染物，制备核-壳结构的硅凝胶固定化菌剂，使芘降解菌在核内保持较高活性且可利用芘生长繁殖，同时硅壳吸附芘和稳定镉，达到高效去除芘和有效稳定镉的双重目的。以“固定化菌剂-芘/镉-土壤”体系为研究主线，在明确菌剂特征和性能的基础上，深入研究芘/镉和载体对菌株活力的影响，理清“固定化菌剂-芘/镉”之间的相互作用规律和微观界面特征；探讨菌株和芘/镉在土壤颗粒与固定化基质间的分配和迁移转化规律，综合分析并揭示硅凝胶固定化菌剂去除土壤中芘和稳定镉的同步作用机制，为开发绿色有效的生物活性材料用于实地复合污染土壤的修复提供新思路和科学依据。

受工业、矿业和农业等人为活动影响，土壤中污染物常以复合形式存在，如多环芳烃PAHs与重金属。重金属不但影响PAHs的微生物修复效率，且可与PAHs通过Cation-π交互作用。因此，研制多功能菌株的强化修复措施并明确其机理对实际污染土壤修复至关重要。本项目以土壤中的菲芘和镉为研究对象：（1） 筛选出两株耐镉的菲芘降解菌，分别为Sphingbium sp. JT-M9-H和Paraburkholderia sp. JT-M8。揭示菌株对镉的耐受性不仅与营养状态有关，且受磷酸根和镉离子水平的驱动，同时受自身基因调控，提出实验室制备菌剂应多方面评估菌株对镉的耐受性和去除性能；（2）开发了三种固定化菌剂，分别为Sawdust@Silica、Cells@ Aggregates和Biochar@LBL，以期吸附和降解有机污染物和稳定土壤重金属，改善土壤理化性质；（3）PAHs降解菌可诱导生物矿化（碳酸钙沉淀，MICP），在MICP过程中，只需加少量尿素，即可促进PAHs的去除和Cd2+的沉淀，同时尿素分解的氮素可作为微生物或作物的营养元素，或可实现边修复边增产的目的；（4）纯化和鉴定酸性槐糖脂ASLs，并研究其对PAHs-Cd复合污染土壤的洗脱，阐释了金属离子和菲之间cation-π作用及土壤类型对洗脱的影响，结果显示ASLs可作为菌株的碳源，促进菌的生长和对四环PAHs芘的降解，且可洗脱土壤中的重金属，实现PAHs-重金属同步净化的目的。综上所述，本项目筛选的多功能菌株可降解PAHs，条件性耐镉，产脲酶诱导碳酸盐沉淀和溶磷等。在净化有机-无机复合污染物的同时，通过生物胶结改善沙质土壤结构。Paraburkholderia sp.菌株被普遍被认为作物益生菌，因此，在综合评估其生态安全和生长环境介质的基础上，研发其固定化菌剂或菌肥，在土壤修复或农业生产方面具有较大的潜力和应用前景。