College of Environmental Science and Engineering, Hunan University, Changsha, Hunan, 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, Hunan, 410082, China.
College of Environmental Science and Engineering, Hunan University, Changsha, Hunan, 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, Hunan, 410082, China.
Environ Pollut. 2022 Nov 15;313:120118. doi: 10.1016/j.envpol.2022.120118. Epub 2022 Sep 7.
The bacteria toxicity of nanoscale zero-valent iron (nZVI) can be changed during its application in water treatment but the toxicity mechanism is still not well understood, particularly under anaerobic conditions. Here, the toxicity of nZVI and its aging products towards Escherichia coli (E. coli) and the mechanisms of extracellular and intracellular reactive oxygen species (ROS) damage were deeply probed in the presence and absence of oxygen in ultrapure water. Under aerobic conditions, the ROS damage primarily caused by the generation of extracellular free •OH can be a major contributor to the toxicity of nZVI to E. coli. By contrast, in anaerobic nZVI treatment system, the intracellular •OH can be quenched by benzoic acid which is a cell permeable quencher and the electron spin resonance (ESR) signals of 5,5-dimethy-1-pyrroline (DMPO)- •OH were evidently observed in system with the addition of F which could desorb the surface •OH into solution. It indicated that the intracellular •OH adsorbed on the particle surface can also play an indispensable role in inactivating cells under anaerobic conditions. Moreover, nZVI can steeply decline the membrane potential, causing severe membrane disruption and therefore resulting in the stronger toxicity in anaerobic conditions. Furthermore, the chemical composition transformation of nZVI and generation of benign iron corrosion products (e.g., FeO, γ-FeO, γ-FeOOH) are mainly responsible for the reduced toxicity with the increasing aging time. These results provide insights into the extracellular and intracellular ROS damage occurred in aerobic and anaerobic nZVI treatment systems, offering more perspective to the risk assessment of nZVI application.
纳米零价铁（nZVI）在水处理中的应用过程中其细菌毒性可能会发生变化，但毒性机制仍不清楚，特别是在厌氧条件下。在此，在超纯水中存在和不存在氧气的情况下，深入探究了 nZVI 及其老化产物对大肠杆菌（E. coli）的毒性及其细胞外和细胞内活性氧（ROS）损伤机制。在有氧条件下，主要由细胞外游离•OH 产生引起的 ROS 损伤可能是 nZVI 对 E. coli 毒性的主要原因。相比之下，在厌氧 nZVI 处理系统中，细胞内•OH 可以被苯甲酸（一种细胞通透的淬灭剂）淬灭，并且在添加 F 的系统中可以观察到 5,5-二甲基-1-吡咯啉（DMPO）-•OH 的电子自旋共振（ESR）信号，F 可以将表面•OH 解吸到溶液中。这表明吸附在颗粒表面上的细胞内•OH 也可以在厌氧条件下在灭活细胞中发挥不可或缺的作用。此外，nZVI 会急剧降低膜电位，导致严重的膜破裂，从而在厌氧条件下产生更强的毒性。此外，nZVI 的化学成分转化和良性铁腐蚀产物（例如，FeO、γ-FeO、γ-FeOOH）的生成主要负责随着老化时间的增加而降低毒性。这些结果深入了解了有氧和厌氧 nZVI 处理系统中发生的细胞外和细胞内 ROS 损伤，为 nZVI 应用的风险评估提供了更多的视角。
