In situ chemical transformations of silver nanoparticles along the water-sediment continuum

Maryam Khaksar, Dianne F. Jolley, Ryo Sekine, Krasimir Vasilev, Bernt Johannessen, Erica Donner, Enzo Lombi

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)

Abstract

In order to accurately assess the potential environmental risk posed by silver nanoparticles (Ag-NPs), their transformation and fate must be investigated in natural systems. This has proven to be very challenging due to the difficulties encountered in retrieving/analyzing NPs dispersed in complex and heterogeneous environmental matrices at relevant (i.e., low) concentrations. In this study, we overcame this challenge by immobilizing functionalized Ag-NPs onto plasma polymerized solid substrates to form "nano in situ deployment devices" (nIDDs). This method allowed us to retrieve and analyze the Ag-NPs after 48 h of direct exposure in freshwater-sediment and saltwater-sediment environments. The type and extent of Ag-NPs transformation was expected to vary along the water-sediment continuum as sediments typically contain steep gradients in solute concentrations and redox potential. To trace the distribution of redox sensitive elements (e.g., Fe, Mn), Diffusive Equilibration in Thin-films (DET) devices were inserted into the sediments alongside the nIDDs. Chemical transformation of the immobilized Ag-NPs across the water-sediment continuum was investigated after retrieval by synchrotron radiation X-ray Absorption Spectroscopy. Linear combination fitting of Ag K-edge X-ray absorption spectra indicated that the chemical transformations of Ag-NPs in both freshwater and saltwater sediments were strongly affected by the redox conditions over the investigated range. Silver bound to reduced sulfur was the principal product of Ag-NP transformations but different extents of transformation were observed for Ag- NPs exposed to different depths in the sediment. These field results add important insights about the transformation of Ag-NPs in heterogeneous environments.

Original languageEnglish
Pages (from-to)318-325
Number of pages8
JournalEnvironmental Science and Technology
Volume49
Issue number1
DOIs
Publication statusPublished - 6 Jan 2015
Externally publishedYes

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