Nov 07, 2013 |
Simple model predicts nanosilver transformations in freshwater sediments
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(Nanowerk News) Silver nanoparticles (AgNPs), an effective antibacterial agent, are a significant and fast-growing application of nanotechnology in consumer goods. The toxicity of AgNPs released to surface waters during the use or disposal of AgNP-containing products will depend on the chemical transformations the nanoparticles undergo in the environment.
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Published in Environmental Science & Technology ("Modeling Nanosilver Transformations in Freshwater Sediments"), researchers from Carnegie Mellon University present a simple one-dimensional diagenetic model for predicting AgNP distribution and silver speciation in freshwater sediments.
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The model is calibrated to data collected from AgNP-dosed large-scale freshwater wetland mesocosms.
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The model predicts that AgNP sulfidation will retard nanoparticle oxidation and ion release. The resultant Ag2S-coated AgNPs are expected to persist and accumulate in sediment downstream from sources of AgNPs.
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Silver speciation and persistence in the sediment depend on the seasonally variable availability of organic carbon and dissolved oxygen. The half-life of typical sulfidized (85% g2S) AgNPs may vary from less than 10 years to over a century depending on redox conditions. No significant difference in silver speciation and distribution is observed between ≥50% Ag2S and 100% Ag2S AgNPs. Formation and efflux of toxic silver ion is reduced in eutrophic systems and maximized in oligotrophic systems.
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