Ion exchange technique (IET) to characterise Ag+ exposure in soil extracts contaminated with engineered silver nanoparticles
Dina Schwertfeger A , Jessica Velicogna A , Alexander Jesmer A , Heather McShane B , Richard Scroggins A and Juliska Princz A C
+ Author Affiliations
- Author Affiliations
A Biological Assessment and Standardisation Section, Environment and Climate Change Canada, 335 River Road, Ottawa, Ontario, K1A 0H3, Canada.
B Department of Natural Resource Sciences, McGill University, 21 111 Lakeshore Road, Sainte Anne de Bellevue, Québec, H9X 3V9, Canada.
C Corresponding author. Email: juliska.princz@canada.ca
Environmental Chemistry 14(2) 123-133 https://doi.org/10.1071/EN16136
Submitted: 30 July 2016 Accepted: 21 November 2016 Published: 11 January 2017
Environmental context. Biosolid-amended soils are likely sinks for manufactured silver nanoparticles, the environmental toxicity of which is believed to be related to the release and accumulation of Ag+ ions. This study demonstrates how an ion exchange technique can be applied to soil extracts to provide Ag+ measurements at low, environmentally relevant levels. The technique is a valuable addition to existing analytical methods for tracking the behaviour of Ag nanoparticles and Ag+ ions in the terrestrial environment.
Abstract. The lack of silver speciation exposure data in toxicity studies investigating the effects of manufactured silver nanoparticles (AgNPs) in natural soil media limits the ability to discern nano-specific effects from effects of the toxic Ag+ form, which may be released from the manufactured AgNPs contained in wastewater, biosolids or soil environment. Using samples containing Ag+ or mixtures of Ag+ and AgNPs, ranging in total Ag concentrations of 10–5 to 10–9 M, and prepared in de-ionised water and filtered soil extracts, the validity of the ion exchange technique (IET) to quantify Ag+ was investigated by comparing measurements to those of an Ag+ ion selective electrode (ISE) and to the dissolved fraction from single particle inductively coupled plasma–mass spectrometry (SP-ICP-MS) analysis (SP-dissolved). When analysing samples in the filtered soil extract, IET and ISE gave comparable results down to 10–7 M, below which Ag+ activities were below the ISE detection limit. For water samples, SP-dissolved values were generally comparable or slightly greater (on average 65 %) compared with IET-Ag+ at all concentrations. The high bias was likely due to inclusion of unresolved particles below the SP-ICP detection limit of 19 nm. However, when analysing samples in the soil extract, SP-dissolved values were on average eight-fold greater than IET-Ag+, highlighting the effect that natural colloidal and dissolved soil constituents have on complexing Ag+, as well as the lack of specificity of the SP-dissolved analysis for the Ag+ species. IET is shown here to be a valid procedure to quantify Ag+ activity in soil extracts, and while the study highlights the limitations of using the SP-dissolved fraction to estimate this biologically relevant Ag fraction, it shows that combined, IET and SP-ICP-MS provide a valuable approach for investigating the behaviour of manufactured AgNPs in different matrixes.
Additional keywords: complex matrix, dissolved silver, ion exchange resin, ion selective electrode, silver free ion activity, SP-ICP-MS, speciation.
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