The emerging case of nanopollutants in the aquatic environment: analytical challenges for the exposure assessment of silver and zinc oxide nanoparticles

Abstract

The growing number of nano-enabled products and technologies suggests likelihood increase of nanopollutants into the environment, a trend that is anticipated to increase further as nanotechnology expands. Nanopollutants are considered a case of emerging environmental contaminants partly due to limited capability to detect and quantify them in environmental matrices. The current paper presents findings from the exposure assessments of silver and zinc oxide nanoparticles (Ag and ZnO NPs) in synthetic and environmental water samples. A suite of commonly used techniques for the determination of size distribution (TEM, zetasizer, NTA), morphology (TEM), stability (UV-vis), dissolution (ICP-MS) and particle concentration (NTA) were applied. For size determination in situ each technique performed fairly well in synthetic media, but all had limitations in river and waste water samples. The presence of background media particles in environmental samples weakened the accuracy of the NTA in deriving both the size distribution and particle number concentration. The determination of soluble metallic forms was influenced by media background concentrations and seperation technique employed. In light of the analytical challenges and the low predicted environmental concentrations of nanopollutants, we propose site specificity for the risk assessment of nano-enabled products.