Nanoscale zero-valent iron ( nZVI) particle is a kind of efficient materials for remediation of many pollutants in the environment; however, the potential toxicity of nano particles might be a risk to small size effects. We investigated the toxicity of nZVI toward gram-negative Escherichia coli, using coated nZVI supported nZVI and bare nZVI, which are widely used for in-situ remediation. Supported nZVI showed the best dispersion performance while bare nZVI the worst. All the three materials showed toxic to Escherichia coli and supported nZVI's toxicity was obviously mitigated. It indicates that the modified nZVI has a physical barrier hindering direct contact between nZVI and bacteria, which is related to electrosteric repulsion. This research emphasizes that the potential risk assessment of nanomaterials are very important before their use.%纳米零价铁是一种高效的环境修复材料,可以处理多种污染物；然而,纳米粒子的尺寸效应可能导致其在自然界中存在潜在毒性风险.选择几种常用包覆型、负载型和裸露的纳米铁,通过大肠杆菌的耐受性实验,比较3种纳米铁的毒性.研究表明,负载型纳米铁的分散性最好,而裸露纳米铁最差.3种纳米铁虽然对大肠杆菌都表现出毒性,但是负载型纳米铁的毒性最小.通过毒性减缓的机理分析,说明纳米铁改性后阻止了纳米颗粒与细菌的直接接触,这是空间位阻效应的作用.研究结果进一步证实了在使用纳米材料前应充分评估潜在毒性和环境效应的重要性.
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