Manufactured Nanoparticles: A New Threat to the Security of Some Groundwater Supplies?

Although climate change is potentially a major threat to the security of water resources, other possible new threats should not be ignored. Nanotechnology is a rapidly expanding industry, and already manufactured nanoparticles (mNPs) are being used in many products. Past experience suggests that use of new chemicals leads to subsurface pollution. The seriousness of this threat depends on two factors: the toxicity of mNPs and their mobility. Many mNPs, particles typically <100 nm across, are composed of metals, metal compounds (e.g. Ag, ZnO, CdSe) or carbon (e.g. carbon nanotubes). An active research area, nanotoxicology is showing toxic effects can occur under some conditions for bacteria, invertebrates, and vertebrates from low ppm concentrations upwards. Factors affecting mNP mobility in groundwater include aggregation, interactions with other particles, attachment to rock, and straining, with behaviour being very dependent on solution chemistry. The limited research available on intact rock samples indicates an encouraging degree of attenuation, at least in matrix flow systems, but field evidence suggests that a small proportion of particles can travel considerable distances.