羧甲基β环糊精与植物油联合同步增效洗脱土壤中PAHs和Cd/Pb的机制

With the rapid speed up of urbanization and industrial shift in China, a lot of organic/inorganic mixed-contaminated soils caused by abandoned steel plants, metallurgic plants, and coking plants are emerged. It is urgent to carry out relevant remediation research. It is widely considered to be promising to employ soil washing technology to remove organic and inorganic pollutants simultaneously from soil. However, currently the combination of chemosynthetic washing solvents are oftern used for the mixed-contaminated soil, the subsequent environment risk can not be ignored. A newly developed and environmentally firendly washing system, which combines carboxymethyl-β-cyclodextrin (CMCD) with vegetable oil, is worthy to be focused on. The present project aims to study the mechanisms involved in the enhanced soil washing technology employing CMCD and vegetable oil as combined washing solvent to removal polycyclic aromatic hydrocarbons (PAHs) - Cd/Pb simultaneously from soil. Firstly, we tend to investigate the capability of CMCD and vegetable oil to solubilize PAHs and complex Cd/Pb. Further, the desorption behaviors of PAHs and Cd/Pb with the co-existence of CMCD and vegetable oil will be systematically studied. Moreover, the main driving force for washed soil ecological restoration will be elucidated by studying soil biological toxicology and microbial biological functioning. The investigation is supposed to provide important theoretical basis and scientific support for the simultaneous washing of PAHs and heavy metals from soils by CMCD-vegetable oil combination.

近年来我国许多钢铁厂、冶金厂和焦化厂等企业生产经营或搬迁导致了大量的PAHs-重金属复合污染土壤，给人体健康和环境安全带来了较严重的潜在威胁，开展针对性的修复研究十分必要。同步增效洗脱土壤中复合污染物是一种具有广泛应用前景的修复技术。但目前针对此类污染土壤，通常采用的是化学合成类洗脱剂组合，其环境风险日益受到重视。新型环境友好型洗脱体系，即羧甲基β环糊精与植物油复配组合值得关注。本项目拟以研究羧甲基β环糊精与植物油联合同步增效洗脱土壤中PAHs和Cd/Pb的机制为主要目标；在探究羧甲基β环糊精与植物油复配体系对PAHs增溶和Cd/Pb络合作用的基础上，揭示复配体系同步增效洗脱土壤中复合污染物的过程与机制，并从土壤生物毒性和微生物生态功能动态变化的角度评价洗脱后土壤环境生态功能的恢复能力，以期为羧甲基β环糊精与植物油联合同步增效洗脱修复PAHs-重金属复合污染土壤提供理论指导和技术支撑。

随着我国城市化进程和产业转移步伐的加快，在很多城市周边或近郊出现了大量由钢铁厂、冶金厂、焦化厂和煤电火力发电厂等企业不规范生产经营和搬迁导致的多环芳烃与重金属复合污染土壤。这些土壤中潜存的高风险复合污染物会成为人类的“化学定时炸弹”，严重威胁人体健康和环境安全，是亟需解决的土壤环境问题。化学洗脱法是一种重要的土壤修复技术。本项目针对南京某焦化厂PAHs-重金属复合污染场地土壤，采用环境友好型的特殊表面活性剂羧甲基β环糊精(CMCD)与葵花籽油水双液相体系进行洗脱修复研究，发现运用升温、超声和连续洗脱等增效手段，在复配条件下土壤中总量PAHs、3环-PAHs、4环-PAHs、5（+6）环-PAHs、Pb、Cd的去除效率分别在62.1%-89.3%、55.3-87.2%、51.4%-81.0%、81.5%-96.3%、44.3%-64.3%、25.6%-53.2%。使用5.0 mL L-1葵花籽油与2.5 g L-1 CMCD优化配方，连续洗脱修复污染土壤。发现随着连续洗脱次数的增加，土壤中复合污染物的去除率也逐渐增加，总量PAHs、3环-PAHs、4环-PAHs、5（+6）环-PAHs、Pb、Cd的去除效率89.3%-99.1%之间；通过Tenax TA树脂连续提取法可知，连续洗脱两次以后，残留在土壤中我的PAHs主要以超慢速解吸组份Fsl存在（比例>98%），同时结合超慢速解吸组份的解吸速率常数进行计算ksl，2.2×10−6 h−1，此部分PAHs完全从土壤颗粒固相解吸至土壤水相的时间至少大于100年；同时结合土壤中重金属形态分级BCR连续提取法可知，连续洗脱2次以后，土壤Pb和Cd稳定性参数IR和再分配能力参数Uts赋存形态已经接近与相同土壤性质清洁土壤中的背景值近似，说明此时土壤中重金属的再分配倾向已经较弱，环境迁移风险已经显著降低。针对洗脱2次后土壤，采用单独或同时种植香根草和接种降解菌，均可以显著降低土壤的生物毒性，提升土著微生物群落功能多样性；并且土壤中3-环，4-环，5（+6）-环和总量PAHs的最大去除量分别是45%，35%，32%和34%；此外，通过高通量测序技术可知该处理条件下，土壤中关于碳氮转化相关的关键功能微生物群落活性得到显著恢复和增强。从而在整体上证明这是一种较为环境友好的集成修复技术。