title: In situ chemical transformations of silver nanoparticles along the water-sediment continuum.
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.
authors.affiliation: Mawson Institute, University of South Australia , Building V, Mawson Lakes Campus, Mawson Lakes, South Australia 5095, Australia.
authors.forename: Maryam
authors.initials: M
authors.lastname: Khaksar
authors.forename: Dianne F
authors.initials: DF
authors.lastname: Jolley
authors.forename: Ryo
authors.initials: R
authors.lastname: Sekine
authors.forename: Krasimir
authors.initials: K
authors.lastname: Vasilev
authors.forename: Bernt
authors.initials: B
authors.lastname: Johannessen
authors.forename: Erica
authors.initials: E
authors.lastname: Donner
authors.forename: Enzo
authors.initials: E
authors.lastname: Lombi
mesh_terms: D005618:Fresh Water / Q000737:chemistry*; D019015:Geologic Sediments / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D012623:Seawater / Q000737:chemistry*; D012834:Silver / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D014874:Water Pollutants, Chemical; D012834:Silver