Environmental context. Silver nanoparticles discharged with municipal wastewater may contaminate surface waters and harm aquatic ecosystems. We applied several analytical techniques to investigate the persistence and transformation of silver nanoparticles in a natural lake environment, and show, through multiple lines of evidence, that they persisted in lake water for several weeks after addition. The nanoparticles were releasing silver ions through dissolution, but these toxic ions were likely binding with natural organic matter in the lake water.Abstract. Silver nanoparticles (AgNPs) may be released into surface waters, where they can affect aquatic organisms. However, agglomeration, dissolution, surface modifications and chemical speciation are important processes that control the toxicity of AgNPs. The purpose of the study was to apply various methods for monitoring the persistence and transformation of AgNPs added to littoral lake mesocosms. Analysis of total Ag showed that the levels in the mesocosms declined rapidly in the first 12 h after addition, followed by a slower rate of dissipation with a half-life (t 1/2 ) of ,20 days. Analysis using single particle ICP-MS (spICP-MS) showed no evidence of extensive homo-agglomeration of AgNPs. The stability of AgNPs was likely due to the low ionic strength and high concentrations of humic-rich dissolved organic carbon (DOC) in the lake water. Analyses by spICP-MS, cloud point extraction (CPE) and asymmetric flow field flow fractionation coupled to ICP-MS (AF4-ICP-MS) all indicated that the concentrations of AgNP decreased over time, and the nanoparticles underwent dissolution. However, the concentrations of dissolved silver, which includes Ag þ , were generally below detection limits when analysed by centrifugal ultrafiltration and spICP-MS. It is likely that the majority of free ions released by dissolution were complexing with natural organic material, such as DOC. An association with DOC would be expected to reduce the toxicity of Ag þ in natural waters. Overall, we were able to characterise AgNP transformations in natural waters at toxicologically relevant concentrations through the use of multiple analytical techniques that compensate for the limitations of the individual methods.
Silver nanoparticles (AgNPs) are currently the most commonly used nanoparticles in consumer products, yet their environmental fate in natural waters is poorly understood. In the present study, we investigated the persistence, transformations and distribution of polyvinylpyrrolidone (PVP) and citrate (CT) coated AgNPs in boreal lake mesocosms dosed either with a 6-week chronic regimen or a one-time pulse treatment at environmentally relevant dosing levels. In the chronic treatments, total Ag (TAg) concentrations reached ∼40% of target concentrations by the end of the experiment, and in the pulsed mesocosms, TAg dissipated slowly, with a half-life of ∼20 days. Sediments and periphyton on the mesocosm walls were an important sink for Ag. We found little effect of AgNP loading and surface coating on the persistence of TAg. There were also no differences between treatments in the degree of agglomeration of AgNPs, as indicated by the accumulation and distribution of Ag in the particulate and colloidal fractions. The low ionic strength and relatively high dissolved organic carbon concentrations in the lake water likely contributed to the relative stability of AgNP in the water column. The low concentrations of dissolved Ag (<1 μg L(-1)) in the size fraction <3 kDaA reflect the importance of natural ligands in controlling the concentrations of Ag released by dissolution of AgNPs. Overall, these data indicate that AgNPs are relatively stable in the tested lake environment and appear to result in quantities of highly toxic ionic Ag(+) that are below our limit of detection.
There is potential for silver nanoparticles (AgNPs) to be released into surface waters and thus affect aquatic organisms. However, agglomeration, dissolution, surface modifications and chemical speciation are important transformation processes that control the toxicity of AgNPs. Analytical methods are needed to determine the size distribution, mass and form of AgNPs and other silver species in natural waters. Cloud point extraction, single particle inductively coupled plasma mass spectrometry (spICP-MS) and asymmetric flow field flow fractionation with on-line ICP-MS (AF4-ICP-MS) are analytical techniques that show potential for quantitative analysis of AgNPs in aquatic matrices at environmentally relevant concentrations. In this review, we discuss the fate processes for AgNPs in natural waters and the analytical methods that can be used to determine the distribution of AgNPs and their transformation products.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.