Speciation and Lability of Ag-, AgCl-, and Ag2S-Nanoparticles in Soil Determined by X-ray Absorption Spectroscopy and Diffusive Gradients in Thin Films

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Sekine, R
Brunetti, G
Donner, E
Khaksar, M
Vasilev, K
Jaemting, AK
Scheckel, KG
Kappen, P
Zhang, H
Lombi, E
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2015
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Abstract

Long-term speciation and lability of silver (Ag-), silver chloride (AgCl-), and silver sulfide nanoparticles (Ag2S-NPs) in soil were studied by X-ray absorption spectroscopy (XAS), and newly developed “nano” Diffusive Gradients in Thin Films (DGT) devices. These nano-DGT devices were designed specifically to avoid confounding effects when measuring element lability in the presence of nanoparticles. The aging profile and stabilities of the three nanoparticles and AgNO3 (ionic Ag) in soil were examined at three different soil pH values over a period of up to 7 months. Transformation of ionic Ag, Ag-NP and AgCl-NPs were dependent on pH. AgCl formation and persistence was observed under acidic conditions, whereas sulfur-bound forms of Ag dominated in neutral to alkaline soils. Ag2S-NPs were found to be very stable under all conditions tested and remained sulfur bound after 7 months of incubation. Ag lability was characteristically low in soils containing Ag2S-NPs. Other forms of Ag were linked to higher DGT-determined lability, and this varied as a function of aging and related speciation changes as determined by XAS. These results clearly indicate that Ag2S-NPs, which are the most environmentally relevant form of Ag that enter soils, are chemically stable and have profoundly low Ag lability over extended periods. This may minimize the long-term risks of Ag toxicity in the soil environment.

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Environmental Science & Technology
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49
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2
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This document is the Post-print of a Published Work that appeared in final form in Environmental Science & Technology, © 2015 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see 10.1021/es504229h
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Other environmental sciences not elsewhere classified
Nanoparticles in soil
X-ray absorption spectroscopy
Neutral to alkaline soils
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