场地修复中纳米零价铁与多氯联苯的共存作用及其细胞毒性效应

Nano-scale zero valent iron (nZVI) has increasingly shown its promise in the remediation of contaminant soil and groundwater because of its characteristic higher adsorption and reduction potential. The ecological risks arising from the high reactivity and cell membrane damage of contaminant-nZVI complex, however, could pose concern to soil biota on remediation sites using nZVI. There is a clear knowledge gap regarding the interactions between nZVI and contaminants and the potential toxic effects thereof to soil biota. This project is aimed at determining cytotoxicity of nZVI mixed with polychlorinated biphenyls (PCBs) and its transient products, and testing the role of surface functional groups of nZVI in the interactions with PCBs. Soil microcosms and cell culture of the earthworm in vitro will be used to compare the dose-response relationship and key factors in systems exposed to the mixtures vs. the complexes of nZVI and PCBs. Ultrafine surface characterization techniques will be used to decipher intra- and extra-cellular molecular conformations and transmembrane transport in the earthworms’coelomocytes in vivo. Further employed with dynamic light scattering, fluorescence spectrum, time-of-flight mass spectrometer and transmission electron microscope, cellular adhesion, transmembrane damage, and binding with intracellular proteins will be examined in the mixture of nZVI and PCBs. This study is attempted to elucidate the effect of the complexes of nZVI-PCBs and the key factors affecting the reactivity of nZVI particles, and determine the dose-response relationships in the oxidative stress and signaling pathway in earthworm as the model organism. The results of this research will greatly enhance our current understanding of the potential adverse effects of nZVI-PCBs on soil biota, and provide scientific basis for the assessment of ecological risk in site remediation using ZVI nanoparticles.

纳米零价铁（nZVI）因吸附和还原双重性，在土壤污染修复中具有广泛应用潜力，但是存在可反应和细胞膜损伤的生态风险。针对有机污染场地纳米修复共存体形态、作用及复合暴露毒性风险问题，拟用nZVI为纳米材料、多氯联苯(PCBs)为有机物、蚯蚓为模式生物，开展非稳态共存体nZVI-PCBs形态识别、相互作用及生物膜界面吸附-脱附过程表征；通过土柱微宇宙装置和蚯蚓体内暴露模拟，比较复合体与混合物的联合作用剂量-效应关系及影响因素；应用蚯蚓腔肠细胞体外暴露试验，剖析复合体的跨膜转运及分子印迹；运用动态光散射、荧光频谱、飞行时间质谱、透射电镜等技术，表征复合体对细胞氧化损伤信号通路影响。阐明蚯蚓暴露模式中nZVI介导PCBs脱氯作用的核-壳复合体吸附-脱附、剂量-效应、及其可反应性影响因子，揭示nZVI-PCBs细胞跨膜转运和细胞氧化损伤信号转导机理，为污染场地修复的生物安全评价和风险调控提供科学依据。

场地修复过程中污染物与土壤无脊椎动物的相互作用剂量-效应关系，是实现安全高效修复目标的科学基础。本课题设计了纳米零价铁(nZVI)-多氯联苯(PCBs)-蚯蚓(赤子爱胜蚓, Eisenia fetida）三元暴露模式试验，研究nZVI介导PCBs脱氯作用的核-壳纳米颗粒表面吸收规律、复合体形态识别、及生物有效性影响，结果表明：（1）赤子爱胜蚓能作为多氯联苯污染场地修复的生物毒性指示，其毒效应生物标志物有超氧化物歧化酶（Superoxide Dismutase, SOD）和过氧化氢酶（Catalase, CAT）；（2）PCBs氯代数影响赤子爱胜蚓毒性效应，PCBs氯代数增加会抑制蚯蚓生长率，呈现∑3-PCBs >PCB101(五氯)>PCB77(DL四氯)>PCB52(四氯)>PCB28(三氯)，最大抑制率达24%；（3）nZVI-PCBs共存对蚯蚓呈协同毒性作用，剂量-效应关系在暴露期2-28天稳定，细胞氧化损伤机制表达显著，氧化应激反应的活性氧(Reactive oxygen species, ROS)和膜脂过氧化指标丙二醛(Malondialdehyde, MDA)随暴露时间和体内PCB富集量而上升，SOD和CAT 14天内呈诱导活性增长、28天呈活性抑制；（4）蚯蚓细胞代谢产物能显著表达nZVI影响PCBs污染致毒通路，运用KEGG(Kyoto Encyclopedia of Genes and Genomes)数据库富集通路分析，糖代谢通路有淀粉和蔗糖代谢、蛋白代谢通路有氨基酸和谷胱甘肽代谢、脂代谢通路有类固醇和脂肪酸生物合成，nZVI主要影响三羧酸循环；（5）蚯蚓肠道DNA及PCR检测，发现nZVI-PCBs共存降低厚壁菌门Firmicutes相对丰富度、提高了变形菌门Proteobacteria丰富度，微生物群落与代谢产物存在相关性，其代谢印迹呈显著差异。