Biotic and Abiotic Interactions in Aquatic Microcosms Determine Fate and Toxicity of Ag Nanoparticles. Part 1. Aggregation and Dissolution

Abstract

To better understand their fate and toxicity in aquatic environments, we compared the aggregation and dissolution behavior of gum arabic (GA) and polyvinylpyrrolidone (PVP) coated Ag nanoparticles (NPs) in aquatic microcosms. There were four microcosm types: surface water; water and sediment; water and aquatic plants; or water, sediment, and aquatic plants. Dissolution and aggregation behavior of AgNPs were examined using ultracentrifugation, ultrafiltration, and asymmetrical flow field flow fractionation coupled to ultraviolet-visible spectroscopy, dynamic and static laser light scattering, and inductively coupled plasma mass spectrometry. Plants released dissolved organic matter (DOM) into the water column either through active or passive processes in response to Ag exposure. This organic matter fraction readily bound Ag ions. The plant-derived DOM had the effect of stabilizing PVP-AgNPs as primary particles, but caused GA-AgNPs to be removed from the water column, likely by dissolution and binding of released Ag ions on sediment and plant surfaces. The destabilization of the GA-AgNPs also corresponded with X-ray absorption near edge spectroscopy results which suggest that 22-28% of the particulate Ag was associated with thiols and 5-14% was present as oxides. The results highlight the potential complexities of nanomaterial behavior in response to biotic and abiotic modifications in ecosystems, and may help to explain differences in toxicity of Ag observed in realistic exposure media compared to simplified laboratory exposures.

Behavior of Ag nanoparticles in soil: Effects of particle surface coating, aging and sewage sludge amendment

“…Because of this, we expect agricultural soils to be a major repository for MNPs and a source of Ag MNPs to aquatic environments through erosion and runoff. It has been shown that aggregation and dissolution behavior of Ag MNPs can have important implications for environmental fate and toxicity Unrine et al, 2012).…”

Highly Dynamic PVP-Coated Silver Nanoparticles in Aquatic Environments: Chemical and Morphology Change Induced by Oxidation of Ag0 and Reduction of Ag+

“…11−15 Meanwhile, AgNPs are highly dynamic in the aqueous solution, 16 and once released into the environment, they would undergo different chemical and morphology transformations during transport, which would in turn greatly affect their final fate, transport, and potential bioavailability and toxicity. 17 In aquatic systems containing abundant electrolytes and Ag-complexing ligands, the undesirable formation of secondary precipitation, 18 cross-linking structures, 19 large aggregates, 20 and recrystallization of small NPs 21 are reported. However, the mechanism for triggering the transformation of AgNPs is still not clear.…”

Detection, characterization and quantification of inorganic engineered nanomaterials: A review of techniques and methodological approaches for the analysis of complex samples

“…Thus preparative centrifugation is not considered an efficient technique for the fractionation of nanoparticles [45]. However, it has proved to be useful for isolation of dissolved species when ultrafiltration fails, which is the case for elements bound by high molecular weight compounds, like dissolved organic matter [46] or proteins, unless nanoparticles exhibit a significant organic corona, which decreases their overall density.…”