State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , Beijing 100085, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Environ Sci Technol. 2017 Dec 19;51(24):14164-14172. doi: 10.1021/acs.est.7b04115. Epub 2017 Dec 5.
The wide use of silver nanoparticles (AgNPs) leads to the increasing release of AgNPs into the environment. Dissolved organic matter (DOM) is a key factor affecting the behaviors and fate of AgNPs in the aquatic environment. However, the mechanisms for the DOM-mediated transformations of AgNPs are still not fully understood. In this study, we investigated the persistence of AgNPs in the aquatic environment in the presence of different concentrations of humic acid (HA) over periods of time up to 14 days. The Ag species were monitored and characterized by absorption spectrometry, transmission electron microscopy (TEM), inductively coupled plasma mass spectrometry (ICP-MS), and multicollector ICP-MS (MC-ICP-MS). Results showed that the long-term persistence of AgNPs in HA-containing water was determined by two critical concentrations of HA. When the HA concentration exceeded a lower critical value, AgNPs could be persistent in the solution, and a large number of AgNPs were formed secondarily from the HA-induced reduction of the Ag ions released from the primary AgNPs, causing a redistribution of the particle size. With the HA concentration above a higher critical value, AgNPs could persist in the solution without a significant change in particle size. Notably, we used Ag isotope fractionation to investigate the transformation mechanism of AgNPs. The natural isotopic analysis by MC-ICP-MS revealed that the size redistribution of AgNPs caused significant Ag isotope fractionation, which gave additional evidence for the proposed mechanisms. This study provides new insights into the environmental fate of engineered AgNPs and highlights the usefulness of stable isotope fractionation in environmental nanotechnology.
纳米银颗粒（AgNPs）的广泛应用导致越来越多的 AgNPs 释放到环境中。溶解有机质（DOM）是影响 AgNPs 在水环境中行为和归宿的关键因素。然而，DOM 介导的 AgNPs 转化机制仍不完全清楚。在这项研究中，我们在长达 14 天的时间内，研究了不同浓度腐殖酸（HA）存在下，AgNPs 在水环境中的持久性。通过吸收光谱、透射电子显微镜（TEM）、电感耦合等离子体质谱（ICP-MS）和多接受器 ICP-MS（MC-ICP-MS）监测和表征 Ag 物种。结果表明，AgNPs 在含有 HA 的水中的长期持久性取决于 HA 的两个关键浓度。当 HA 浓度超过较低临界值时，AgNPs 可以在溶液中保持稳定，大量 AgNPs 从初级 AgNPs 释放的 Ag 离子的 HA 诱导还原中形成二次颗粒，导致颗粒尺寸重新分布。当 HA 浓度高于较高临界值时，AgNPs 可以在溶液中保持稳定，而颗粒尺寸没有明显变化。值得注意的是，我们使用 Ag 同位素分馏来研究 AgNPs 的转化机制。MC-ICP-MS 的自然同位素分析表明，AgNPs 的尺寸重新分布导致显著的 Ag 同位素分馏，为所提出的机制提供了额外的证据。这项研究为工程 AgNPs 的环境归宿提供了新的见解，并强调了稳定同位素分馏在环境纳米技术中的有用性。
