Risks from Renegade Nanoparticles during field deployments within NanoRem

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The aim of NanoRem is to support and develop the appropriate use of nanotechnology for contaminated soil and groundwater remediation. NanoRem focuses on facilitating practical, economic and exploitable nanotechnology for in-situ remediation. This can only be achieved in parallel with a comprehensive understanding of the environmental risk-benefit balance for the use of nanoparticles (NPs).

One of NanoRem’s objectives is to provide field evidence of the safe and effective deployment of NPs to remediate polluted groundwater. The health and safety aspects of injecting nanoparticles do not pose a particularly novel challenge. However it is necessary to consider the potential risks of injecting NPs into groundwater. Risk assessment specialists from Nottingham-based SME Land Quality Management (LQM) developed a protocol to allow the NanoRem field trials to evaluate the risks posed by NPs that do not get consumed in the remediation process. The fate, transport and toxicity of these so called renegade NPs was considered during an expert elicitation workshop organised by LQM at its University of Nottingham Innovation Park offices. The workshop outcomes supported with evidence from the literature formed the basis for a simple protocol for field trial sites to use to evaluate the risk posed by their NP deployment and demonstrate to regulators the trials would be safe.

LQM’s work focused on the NanoRem NPs. While these NPs could have a significant toxicity, they are less potent than nano Silver (nano Ag). They are likely to interact with the aquifer matrix, each other and groundwater to rapidly cease to be mobile NPs. They are therefore likely to be difficult to penetrate into the aquifer more than a few metres from the point of injection.

For an environmental risk to exist all of the following must be present: a source of contamination (S), a receptor (R) and a pathway(s) (P) linking the two - i.e. a contaminant linkage (S-P-R) and such linkages are shown on the Conceptual Site Model (CSM) see Figure 1.

A CSM addressing the possible risk from renegade nanoparticles needs to be created separately from, and is in addition to the CSM which should already have been developed for the contamination problem at the site. For the pre-deployment risk assessment for NP injection, the NP themselves are considered as the source, with the CSM used as a tool to consider whether there are potential pathways for NPs to relevant receptors.

Receptors that could be affected by NPs include: human health, surface and ground water, or ecosystems, although for some of these the potential exposure scenarios are unlikely. Despite the uncertainties, LQM identified a range of circumstances that indicate NP can be safely deployed. These include an absence of receptors, where a site has pathway interruption though (e.g. a down gradient Permeable Reactive Barrier) or the limited NP transport means the receptor would not be reached by fugitive NP.

Overall while there are considerable uncertainties particularly with regards to the transport of NanoRem NPs the ability of NP to penetrate far into the formation is likely to be very limited. At this stage such a protective situation is welcome. Once the results of the field trials are available, LQM will update the risk assessment protocol for eventual publication and consideration for wider take up.

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