Silver nanoparticles (AgNPs) are expected to accumulate in sediments near points of release. The toxicity of antibacterial AgNPs released to surface waters during the use or disposal of AgNP-containing products will therefore depend on the chemical transformations the nanoparticles undergo in sediments.  We present a one-dimensional diagenetic model for predicting AgNP distribution and silver speciation in freshwater sediments.  The model is calibrated to data collected from a AgNP-dosed freshwater wetland mesocosms.  Results suggest AgNP sulfidation will retard nanoparticle oxidation and ion release. Importantly, silver speciation and AgNP persistence in the sediment depend on the seasonally variable availability of organic carbon and dissolved oxygen, such that free ion formation is reduced in eutrophic systems and maximized in oligotrophic systems.  The half-life of typical sulfidized (85% Ag2S) AgNPs may vary from less than ten years to over a century depending on redox conditions. AgNPs entering sediments that are already =50% Ag2S behave identically.

Modeling nanosilver transformations in freshwater sediments

248th National Meeting (2014)

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