ZnO nanoparticles (NPs) form binary mixtures of ZnO particles and released Zn2+ in the environment, and the quantitative contributions of these components to toxicity are still uncertain. Herein, quantitative contribution of ZnO particle and Zn2+ to cytotoxicity of ZnO NPs to Escherichia coli were determined during 48 h bioassay. The cytotoxicity and mechanisms of ZnO NPs were dynamic and affected by ionic strength, Fe3+, humic acid, and temperature due to the unfixed ZnO particle:Zn2+ ratio. ZnO NPs and ZnO bulk particles (BPs) had comparable cytotoxicity but distinct cytotoxic mechanisms. ZnO NPs cytotoxicity arises mainly from ZnO particles for 3 h and from Zn2+ afterwards (8-48 h). The cytotoxicity of ZnO BPs depends predominantly on ZnO particles for 12 h and on Zn2+ from 24 to 48 h. The cytotoxicity of ZnO NPs and BPs is partially attributable to Zn accumulation, and dependent on ZnO particle:Zn2+ ratio. The linear regressions of acute toxicity for ZnO NPs vs. BPs and Zn2+ yielded excellent r2 (0.9994 and 0.9998) from literature data and good r2 (≥ 0.714) under certain environmental factors, which can be applied to assess environmental risk of ZnO NPs. Furthermore, dynamic cytotoxicity and mechanisms should be seriously considered during the environmental risk assessment of ZnO NPs.

中文翻译：

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ZnO纳米颗粒和散装颗粒对大肠杆菌的动态细胞毒性：从未固定的ZnO颗粒与Zn2 +的比例观察。

ZnO纳米颗粒（NPs）形成ZnO颗粒的二元混合物，并在环境中释放出Zn2 +，这些组分对毒性的定量贡献仍不确定。本文中，在48小时的生物测定过程中，确定了ZnO颗粒和Zn2 +对ZnO NPs对大肠杆菌的细胞毒性的定量贡献。ZnO NPs的细胞毒性和机制是动态的，并且由于未固定的ZnO颗粒：Zn2 +的比例而受到离子强度，Fe3 +，腐殖酸和温度的影响。ZnO NP和ZnO大颗粒（BP）具有可比的细胞毒性，但细胞毒性机制却不同。ZnO NPs的细胞毒性主要由3小时的ZnO颗粒引起，其后由8至48 h的Zn2 +引起。ZnO BPs的细胞毒性主要取决于ZnO颗粒持续12 h和Zn2 +持续24至48 h。ZnO NPs和BPs的细胞毒性部分归因于Zn的积累，并取决于ZnO颗粒：Zn2 +的比例。ZnO NPs与BPs和Zn2 +的急性毒性的线性回归从文献数据得出了极好的r2（0.9994和0.9998），在某些环境因素下产生了良好的r2（≥0.714），可用于评估ZnO NPs的环境风险。此外，在对ZnO NPs进行环境风险评估时，应认真考虑动态细胞毒性和机制。