Fate and transformation of silver nanoparticles in urban wastewater systems.
TL;DR: Ag-NP discharged to the wastewater stream will become sulfidized to various degrees in the sewer system and are efficiently transported to the WWTP, but primarily depending on the size the Ag-NP, may not be complete.
About: This article is published in Water Research.The article was published on 2013-08-01. It has received 397 citations till now. The article focuses on the topics: Wastewater & Sewage treatment.
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TL;DR: Recent achievements in the field of nano-ecotoxicology in both aquatic and terrestrial systems are highlighted but also substantial gaps that require further attention in the future are referred to.
Abstract: Nanoparticles serve various industrial and domestic purposes which is reflected in their steadily increasing production volume. This economic success comes along with their presence in the environment and the risk of potentially adverse effects in natural systems. Over the last decade, substantial progress regarding the understanding of sources, fate, and effects of nanoparticles has been made. Predictions of environmental concentrations based on modelling approaches could recently be confirmed by measured concentrations in the field. Nonetheless, analytical techniques are, as covered elsewhere, still under development to more efficiently and reliably characterize and quantify nanoparticles, as well as to detect them in complex environmental matrixes. Simultaneously, the effects of nanoparticles on aquatic and terrestrial systems have received increasing attention. While the debate on the relevance of nanoparticle-released metal ions for their toxicity is still ongoing, it is a re-occurring phenomenon that inert nanoparticles are able to interact with biota through physical pathways such as biological surface coating. This among others interferes with the growth and behaviour of exposed organisms. Moreover, co-occurring contaminants interact with nanoparticles. There is multiple evidence suggesting nanoparticles as a sink for organic and inorganic co-contaminants. On the other hand, in the presence of nanoparticles, repeatedly an elevated effect on the test species induced by the co-contaminants has been reported. In this paper, we highlight recent achievements in the field of nano-ecotoxicology in both aquatic and terrestrial systems but also refer to substantial gaps that require further attention in the future.
529 citations
TL;DR: This study shows that it is important to understand in detail how silver and silver nanoparticles exert their toxicity and to understand how bacteria acquire silver resistance, to lead to a better understanding of the impact on human health and ecosystems.
Abstract: This review gives a comprehensive overview of the widespread use and toxicity of silver compounds in many biological applications. Moreover, the bacterial silver resistance mechanisms and their spread in the environment are discussed. This study shows that it is important to understand in detail how silver and silver nanoparticles exert their toxicity and to understand how bacteria acquire silver resistance. Silver ions have shown to possess strong antimicrobial properties but cause no immediate and serious risk for human health, which led to an extensive use of silver-based products in many applications. However, the risk of silver nanoparticles is not yet clarified and their widespread use could increase silver release in the environment, which can have negative impacts on ecosystems. Moreover, it is shown that silver resistance determinants are widely spread among environmental and clinically relevant bacteria. These resistance determinants are often located on mobile genetic elements, facilitating their spread. Therefore, detailed knowledge of the silver toxicity and resistance mechanisms can improve its applications and lead to a better understanding of the impact on human health and ecosystems.
424 citations
Cites background from "Fate and transformation of silver n..."
...The use of sewage sludge as fertilizer or as organic soil improver can also lead to the spread of silver in the environment (Kaegi et al. 2013)....
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TL;DR: The overall aim of this review is to examine methods for the capture and detection of AgNPs, potential toxicity and transmission routes in the aquatic environment.
392 citations
Cites background from "Fate and transformation of silver n..."
...Kalbassi et al. (2013) demonstrated a particle size influenced, dose dependant toxicity on two day old Rainbow Trout (Oncorhynchus mykiss) alevin and juveniles (15.47 g ± 0.83 g) treated for 4 days with colloidal silver and AgNPs in suspended powder forms....
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...Several studies have looked at the influence of various physical characteristics of AgNP such as size, coating and charge on their toxicity (Baumann et al., 2014; Blinova et al., 2013; Choi and Hu, 2008; El Badawy et al., 2011; Ivask et al., 2014; Kalbassi et al., 2013; Silva et al., 2014)....
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...Kalbassi et al. (2013) demonstrated that the powdered suspensions of AgNP leads to increased agglomeration and reduced toxicity by investigating the effect of agglomeration on the toxicity to Rainbow Trout (Oncorhynchus mykiss)....
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TL;DR: It is suggested that even partial sulfidation of AgNP will decrease the toxicity of AgNPs relative to their pristine counterparts, and the presence of chloride in the exposure media strongly affects the toxicity results by affecting Ag speciation.
Abstract: Nanomaterials are highly dynamic in biological and environmental media. A critical need for advancing environmental health and safety research for nanomaterials is to identify physical and chemical transformations that affect the nanomaterial properties and their toxicity. Silver nanoparticles, one of the most toxic and well-studied nanomaterials, readily react with sulfide to form Ag(0)/Ag2S core–shell particles. Here, we show that sulfidation decreased silver nanoparticle toxicity to four diverse types of aquatic and terrestrial eukaryotic organisms (Danio rerio (zebrafish), Fundulus heteroclitus (killifish), Caenorhabditis elegans (nematode worm), and the aquatic plant Lemna minuta (least duckweed)). Toxicity reduction, which was dramatic in killifish and duckweed even for low extents of sulfidation (about 2 mol % S), is primarily associated with a decrease in Ag+ concentration after sulfidation due to the lower solubility of Ag2S relative to elemental Ag (Ag0). These results suggest that even partial ...
376 citations
TL;DR: The goal of this present review is to use knowledge on the life cycle of nano-products to derive possible transformations common ENPs in nano- products may undergo based on how these products will be used by the consumer and eventually discarded.
333 citations
Cites background from "Fate and transformation of silver n..."
...Asmuch of ENPs are destined eventually to flow throughwastewater treatment facilities after nano-product use, the release of ENPs from these plants has also been explored (Kiser et al., 2009; Westerhoff et al., 2011; Kaegi et al., 2011, 2013)....
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References
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TL;DR: A software package for the analysis of X-ray absorption spectroscopy (XAS) data is presented, based on the IFEFFIT library of numerical and XAS algorithms and is written in the Perl programming language using the Perl/Tk graphics toolkit.
Abstract: A software package for the analysis of X-ray absorption spectroscopy (XAS) data is presented. This package is based on the IFEFFIT library of numerical and XAS algorithms and is written in the Perl programming language using the Perl/Tk graphics toolkit. The programs described here are: (i) ATHENA, a program for XAS data processing, (ii) ARTEMIS, a program for EXAFS data analysis using theoretical standards from FEFF and (iii) HEPHAESTUS, a collection of beamline utilities based on tables of atomic absorption data. These programs enable high-quality data analysis that is accessible to novices while still powerful enough to meet the demands of an expert practitioner. The programs run on all major computer platforms and are freely available under the terms of a free software license.
12,505 citations
TL;DR: A review of the antibacterial effects of silver nanomaterials, including proposed antibacterial mechanisms and possible toxicity to higher organisms, is presented in this paper, where the authors suggest that further research is warranted given the already widespread and rapidly growing use of silver nanoparticles.
Abstract: Here, we present a review of the antibacterial effects of silver nanomaterials, including proposed antibacterial mechanisms and possible toxicity to higher organisms. For purpose of this review, silver nanomaterials include silver nanoparticles, stabilized silver salts, silver–dendrimer, polymer and metal oxide composites, and silver-impregnated zeolite and activated carbon materials. While there is some evidence that silver nanoparticles can directly damage bacteria cell membranes, silver nanomaterials appear to exert bacteriocidal activity predominantly through release of silver ions followed (individually or in combination) by increased membrane permeability, loss of the proton motive force, inducing de-energization of the cells and efflux of phosphate, leakage of cellular content, and disruption DNA replication. Eukaryotic cells could be similarly impacted by most of these mechanisms and, indeed, a small but growing body of literature supports this concern. Most antimicrobial studies are performed in simple aquatic media or cell culture media without proper characterization of silver nanomaterial stability (aggregation, dissolution, and re-precipitation). Silver nanoparticle stability is governed by particle size, shape, and capping agents as well as solution pH, ionic strength, specific ions and ligands, and organic macromolecules—all of which influence silver nanoparticle stability and bioavailability. Although none of the studies reviewed definitively proved any immediate impacts to human health or the environment by a silver nanomaterial containing product, the entirety of the science reviewed suggests some caution and further research are warranted given the already widespread and rapidly growing use of silver nanomaterials.
2,467 citations
TL;DR: This work suggests that AgNP morphological properties known to affect antimicrobial activity are indirect effectors that primarily influence Ag(+) release, and antibacterial activity could be controlled by modulating Ag(+ release, possibly through manipulation of oxygen availability, particle size, shape, and/or type of coating.
Abstract: For nearly a decade, researchers have debated the mechanisms by which AgNPs exert toxicity to bacteria and other organisms. The most elusive question has been whether the AgNPs exert direct “particle-specific” effects beyond the known antimicrobial activity of released silver ions (Ag+). Here, we infer that Ag+ is the definitive molecular toxicant. We rule out direct particle-specific biological effects by showing the lack of toxicity of AgNPs when synthesized and tested under strictly anaerobic conditions that preclude Ag(0) oxidation and Ag+ release. Furthermore, we demonstrate that the toxicity of various AgNPs (PEG- or PVP- coated, of three different sizes each) accurately follows the dose–response pattern of E. coli exposed to Ag+ (added as AgNO3). Surprisingly, E. coli survival was stimulated by relatively low (sublethal) concentration of all tested AgNPs and AgNO3 (at 3–8 μg/L Ag+, or 12–31% of the minimum lethal concentration (MLC)), suggesting a hormetic response that would be counterproductive t...
1,785 citations
TL;DR: Variable leaching rates among sock types suggests that the sock manufacturing process may control the release of silver, and physical separation and ion selective electrode (ISE) analyses suggest that both colloidal and ionic silver leach from the socks.
Abstract: Manufacturers of clothing articles employ nanosilver (n-Ag) as an antimicrobial agent, but the environmental impacts of n-Ag release from commercial products are unknown. The quantity and form of the nanomaterials released from consumer products should be determined to assess the environmental risks of nanotechnology. This paper investigates silver released from commercial clothing (socks) into water, and its fate in wastewater treatment plants (WWTPs). Six types of socks contained up to a maximum of 1360 µg-Ag/g-sock and leached as much as 650 µg of silver in 500 mL of distilled water. Microscopy conducted on sock material and wash water revealed the presence of silver particles from 10 to 500 nm in diameter. Physical separation and ion selective electrode (ISE) analyses suggest that both colloidal and ionic silver leach from the socks. Variable leaching rates among sock types suggests that the sock manufacturing process may control the release of silver. The adsorption of the leached silver to WWTP biom...
1,703 citations
TL;DR: An empirical kinetic law is proposed that reproduces the observed effects of dissolution time, pH, humic/fulvic acid content, and temperature observed here in the low range of nanosilver concentration most relevant for the environment.
Abstract: Many important aspects of nanosilver behavior are influenced by the ionic activity associated with the particle suspension, including antibacterial potency, eukaryotic toxicity, environmental release, and particle persistence. The present study synthesizes pure, ion-free, citrate-stabilized nanosilver (nAg) colloids as model systems, and measures their time-dependent release of dissolved silver using centrifugal ultrafiltration and atomic absorption spectroscopy. Ion release is shown to be a cooperative oxidation process requiring both dissolved dioxygen and protons. It produces peroxide intermediates, and proceeds to complete reactive dissolution under some conditions. Ion release rates increase with temperature in the range 0−37 °C, and decrease with increasing pH or addition of humic or fulvic acids. Sea salts have only a minor effect on dissolved silver release. Silver nanoparticle surfaces can adsorb Ag+, so even simple colloids contain three forms of silver: Ag0 solids, free Ag+ or its complexes, an...
1,571 citations