纳米氧化锌水环境转化过程对藻类毒性影响及其机制研究

With the rapid developments in nanotechnology, the potential impact of nanomaterials on the environment and biology has received increasing attention. Many studies in nanotoxicology showed that the toxicity effect of nanomaterial is significantly influenced by environmental processes, and lead to the toxicity difference to original nanoparticles. But the inherent impact mechanism of toxic effects has not been fully elucidated, which may lead to unreasonable evaluation of nonmaterial environmental safety. Zinc oxide nanoparticles (ZnO NPs), because of their unique physical and chemical properties make them attracted much attention after the appearance of carbon nonmaterial, are important industrial materials and used widely in many fields. Also, ZnO NPs are ion-shedding nanoparticles, and zinc ions produce important and potent effects that differ from those of other metal or metal oxide nanomaterials. Therefore, ZnO NPs was selected in this project, the aquatic ecosystem primary producer algae was selected as the tested organism. To qualitative and quantitative analysis of the conversion process of ZnO NPs in aquatic environment using spectroscopy combined with relevant technology, including zinc ion releasing behavior, the species and contents of neoformation transformed from ZnO NPs in the environment. The differences of algal toxicity effect between the original ZnO NPs and transformed ZnO NPs in the environment will be studied. The mechanisms of algal toxicity induced by ZnO NPs, neoformation and analogue will be differentiated. The variation of toxicity to algal cells induced by ZnO NPs transformation in aquatic environment will be verified and researched deeply. This work will provide a theoretical and experimental foundation for the scientific and reasonable evaluation of the ecological safety of nanomaterials in the real environment.

随着纳米科技迅速发展，纳米材料对环境和生物潜在影响已受到广泛关注。纳米毒理学研究表明，环境过程对纳米材料毒性效应影响显著，使其毒性区别于原始态纳米材料，但环境过程对毒性效应影响规律尚未完全阐明，可能会导致纳米材料环境安全性的不合理评价。纳米氧化锌因其独特的理化性质使其成为继碳纳米材料之后备受关注的多功能材料，又因其易于释放锌离子使其毒性有别于其它金属氧化物纳米材料。因此，本项目选用纳米氧化锌，以水生生态系统初级生产者藻类为受试生物，利用光谱结合相关技术，对纳米氧化锌在水环境中转化过程进行分析，明确锌离子释放规律、转化生成物的种类、性质、含量等；通过检测纳米氧化锌转化前后对藻类毒性的差异，明确转化过程对毒性效应的影响；利用转化物单独或复合作用对藻类毒性差异，探究转化物组分对最终毒性效应贡献，阐明环境转化对藻类毒性影响的机制，为科学、合理评价真实水环境中纳米材料生态安全性奠定理论和实验基础。

纳米材料广泛应用对环境和生物的潜在影响已受到广泛关注。纳米毒理学研究表明，环境转化过程对纳米材料毒性效应影响显著，使其毒性区别于原始状态纳米材料，但环境转化特性对毒性效应的影响规律及机制研究仍然较为匮乏。本项目针对纳米材料环境安全性研究的关键科学问题，选取典型纳米材料纳米氧化锌为研究对象，以藻类为受试生物，探究纳米氧化锌在模拟水体中赋存状态的转化规律，揭示环境转化过程对毒性效应影响及机制。我们研究发现，纳米氧化锌在含磷水体中发生复杂的物理化学转化，随水体磷含量的增加，纳米氧化锌先部分转变成晶体状磷酸锌，再转变成无定型磷酸锌。藻类毒性效应结果表明，原始状态纳米氧化锌毒性主要源自其释放的锌离子，转化后纳米氧化锌生成了低毒性的磷酸锌，致使毒性效应显著区别于原始状态纳米氧化锌。结合光合作用相关基因表达分析，揭示了纳米氧化锌理化转化对藻类光合作用产生影响是毒性效应差异的重要原因。纳米氧化锌在含硫水体中转化显著改变了纳米材料晶体结构，使纳米颗粒表面边缘模糊化，形成核壳结构，转化生成纳米硫化锌附着在颗粒表面，其含量随着硫含量增加而增大。毒性效应检测结果显示，硫化后纳米氧化锌对藻类毒性效应与原始状态纳米氧化锌相比有显著差异。叶绿素a含量、光合效率、电子传递速率的检测结果说明，硫化的纳米氧化锌能改变藻细胞内光合色素含量、光合效率及光合电子传递速率，结合纳米氧化锌硫化转化的特性，提示锌离子溶出释放及转化产物纳米硫化锌分别在处理不同时期对毒性效应起主导作用，致使藻类毒性效应发生相应变化。纳米氧化锌在自来水、藻类培养基、水库水样和巢湖水样中溶出锌离子的浓度差异显著。藻类毒性效应结果显示，与原始纳米氧化锌相比上述四种水样中转化后样品对藻类生长抑制效率不同，以水库水样抑制效率最为显著。本项目为系统评价纳米材料对环境和生物潜在影响，指导纳米材料合理应用以及促进纳米科技健康发展提供理论依据和实验基础。