Transformations of silver nanoparticles in wastewater effluents: links to Ag bioavailability

Abstract

As a result of the burgeoning nanotechnology industry, the number of uses of engineered silver nanoparticles (Ag NPs) in consumer products has risen significantly in recent years.Despite their utility as anti-bacterial agents, the 'nano-scale' properties of these materials may lead to eco-toxicological problems when they end up in the environment. Wastewater effluents represent one of the main routes through which Ag NPs can reach an aquatic environment, where they may potentially interact with aquatic life. However, in wastewaters, Ag NPs may undergo different chemical and physical transformations, which may alter the potential toxicity of these NPs towards aquatic organisms. The main objectives of this study are to characterize the Ag NPs in wastewater effluents and then to assess their interactions with a model organism, the green alga Chlamydomonas reinhardtii.Experiments were conducted to distinguish the effect(s) of the wastewater matrix on the dissolution of Ag NPs and to determine whether the transformed NPs or the dissolved Ag species would be most bioavailable to C. reinhardtii. It was shown that in environmental matrices such as wastewater, the bioavailability of Ag + could be significantly or completely reduced-a Nous avons étudié l'effet de la matrice des eaux usées sur la dissolution des Ag NPs et la biodisponibilité des différentes formes (particulaire et dissoute) des Ag NPs pour C. reinhardtii.Dans les matrices environnementales telles que les eaux usées la biodisponibilité de Ag + serait réduite de façon significative, si ce n'est complète; une conclusion qui va à l'encontre les résultats des études similaires faites dans des matrices biologiques simples. Cette réduction

Ecotoxicological Effects of Transformed Silver and Titanium Dioxide Nanoparticles in the Effluent from a Lab-Scale Wastewater Treatment System

“…reinhardtii 19 and the protective effects of background effluent were observed towards Cu interference with zebrafish hatching 15 . Furthermore, a decrease in the bioavailability of Ag from AgNO 3 -exposed algae (C. reinhardtii) was observed in wastewaters, and suggested to be due to the presence of ligands 12 . It has been previously demonstrated that sulfidation 53 , the presence of natural organic matter 57 and thiol-or selenide-containing compounds such as cysteine 58 can reduce the Ag NP dissolution rate and lead to protective effects due to Ag + complexation and decreased bioavailability 59,60 , partially explaining the reduced toxicity of Ag NPs spiked in background effluent.…”

“…Nanoparticles undergo a combination of physical and chemical transformations in environmental media (e.g. wastewaters) 10 that may influence their behavior, bioavailability and toxicity 11,12 .…”

“…Furthermore, studies using a pilot WWTP fed with municipal wastewater spiked with Ag NPs, showed a transformation to Ag 2 S while some of the Ag NPs detected in the effluent were still in the pristine metallic form 14 . Even though most NPs present in the natural environment are likely to have undergone some form of physicochemical transformation, very few effects studies have employed transformed NPs [15][16][17] or NPs in environmentally relevant media such as wastewaters 12,18,19 . One recent study has shown that Cu NP transformation through a septic tank led to a lack of toxicity in a zebrafish embryo hatching assay 15 .…”

Effects of human serum on the stability and cytotoxicity of silver nanoparticles

“…Silver nanoparticles are routinely used as anti-microbial agents [7][8][9][10][11]; however, the toxicity data for silver particles in mammalian cell lines [12][13][14][15][16] and in animal studies [17][18][19][20][21], remains inconclusive with respect to potential hazards that the particles might pose. Silver nanoparticles are particularly challenging to get accurate reproducible data for because they can rapidly dissolve in aqueous media under some conditions, or agglomerate and ultimately precipitate under other aqueous conditions [22][23][24][25][26][27][28]. This acute sensitivity to media conditions, is compounded by the fact that they behave very differently in different cell lines [29].…”

Anions influence the extraction of rutile nanoparticles from synthetic and lake water

“…Wastewater treatment operations with the highest potential for removing NPs are primary and secondary sedimentation tanks. 33,34 However, wastewater contains surfactants and natural organic matter, which may hinder the removal of NPs from wastewater. 7,35,36 The types of ions, ionic strength, pH, alkalinity, and presence of natural organic matter also inuences the process.…”