Toxicity of NZVI to Soil-Dwelling Organisms: Measuring Dose in Soils

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Adding nanoengineered materials to brownfield soils for remediation would need to consider theenvironmental risks posed by these materials relative to the risks of the contaminant that is being remediated.Nano Zero-Valent Iron Particles (nZVI) have been used as a soil remediation method for more than a decade todegrade or immobilize organic and inorganic soil contaminants, halogenated organic compounds, PAHs,pesticides and heavy metals. The limitation to its broader use in Ontario, is that there is little knowledge of theenvironmental impact of the use of nZVI on soil ecosystems. Due to the unique properties associated withnanoparticles and the application of nZVI to soil as a means of remediation, environmental risk assessmentsmust be performed. However, there is potential for persistence in the environment of any formed ortransformed material, bioaccumulation, and toxicity to microbes and organisms living in the soil could result.So far, this is poorly characterized for nZVI in soils, the barrier to which is that high quality toxicity studiesmust report measured rather than nominal exposure concentrations, and methods for quantifying nZVI incomplex media are not well established. There are a number of microscopic and spectroscopic methods thatcan detect nZVI, the bigger challenge is quantification (Shi et al., 2015). Once capacity for quantification areestablished, the effect on ecotoxicity of the various surfactants on commercially available forms of nZVI can beidentified. The methodologies for measuring nZVI, to be applied in this study are Nuclear Magnetic Resonance(NMR), and the chemical redox probe indigo disulphonate (I2S). These will be used to measure NZVI in soilpore water, extracted from the experimental media by centrifugation. The benefit to Canada is that strategicrisk assessments of nZVI toxicity to soil dwelling organisms specific to Canada have yet to be conducted. Soilorganisms such as earthworms, plants, and invertebrates may be exposed to nZVI, and due to its small size,anaerobic bacteria in the soil may also be impacted significantly. Such investigation would allow Canada toadopt the lead position in this field and allow for informed decisions to be made concerning regulations