Surface and Aqueous Geochemistry Group, Department of Geological & Environmental Sciences, Stanford University, Stanford, California 94305-2115, United States.
Environ Sci Technol. 2012 Jul 3;46(13):6900-14. doi: 10.1021/es2037405. Epub 2012 Feb 29.
Silver nanoparticles (Ag-NPs) readily transform in the environment, which modifies their properties and alters their transport, fate, and toxicity. It is essential to consider such transformations when assessing the potential environmental impact of Ag-NPs. This review discusses the major transformation processes of Ag-NPs in various aqueous environments, particularly transformations of the metallic Ag cores caused by reactions with (in)organic ligands, and the effects of such transformations on physical and chemical stability and toxicity. Thermodynamic arguments are used to predict what forms of oxidized silver will predominate in various environmental scenarios. Silver binds strongly to sulfur (both organic and inorganic) in natural systems (fresh and sea waters) as well as in wastewater treatment plants, where most Ag-NPs are expected to be concentrated and then released. Sulfidation of Ag-NPs results in a significant decrease in their toxicity due to the lower solubility of silver sulfide, potentially limiting their short-term environmental impact. This review also discusses some of the major unanswered questions about Ag-NPs, which, when answered, will improve predictions about their potential environmental impacts. Research needed to address these questions includes fundamental molecular-level studies of Ag-NPs and their transformation products, particularly Ag(2)S-NPs, in simplified model systems containing common (in)organic ligands, as well as under more realistic environmental conditions using microcosm/mesocosm-type experiments. Toxicology studies of Ag-NP transformation products, including different states of aggregation and sulfidation, are also required. In addition, there is the need to characterize the surface structures, compositions, and morphologies of Ag-NPs and Ag(2)S-NPs to the extent possible because they control properties such as solubility and reactivity.
银纳米颗粒（Ag-NPs）在环境中很容易发生转化，这会改变它们的性质，并影响它们的迁移、归宿和毒性。在评估 Ag-NPs 的潜在环境影响时，必须考虑到这些转化。本文讨论了 Ag-NPs 在各种水相环境中的主要转化过程，特别是金属 Ag 核与（无机）配体反应引起的转化，以及这些转化对物理化学稳定性和毒性的影响。热力学论点被用来预测在各种环境情景中哪种形式的氧化银将占主导地位。在自然系统（淡水和海水）以及废水处理厂中，银与硫（有机和无机）强烈结合，Ag-NPs 预计将在这些地方浓缩并随后释放。Ag-NPs 的硫化导致其毒性显著降低，这是由于硫化银的溶解度较低，从而可能限制其短期的环境影响。本文还讨论了一些关于 Ag-NPs 的未解决的重要问题，这些问题的答案将有助于提高对其潜在环境影响的预测。需要开展的研究包括在含有常见（无机）配体的简化模型系统中，对 Ag-NPs 及其转化产物（特别是 Ag(2)S-NPs）进行基础的分子水平研究，以及在使用微宇宙/中宇宙类型实验的更现实的环境条件下进行这些研究。还需要开展 Ag-NP 转化产物的毒理学研究，包括不同的聚集状态和硫化状态。此外，还需要尽可能地对 Ag-NPs 和 Ag(2)S-NPs 的表面结构、组成和形态进行表征，因为它们控制着溶解度和反应性等性质。
