Analysis of engineered nanomaterials (Ag, CeO_2 and Fe_2O_3) in spiked surface waters at environmentally relevant particle concentrations

摘要

Quantification of engineered nanomaterials (ENMs) concentrations in surface waters remains one of the key challenges in environmental nanoscience and nanotechnology. A promising approach to estimate metal and metal oxide ENM concentrations in complex environmental samples is based on the increase in the elemental ratios of ENM-contaminated samples relative to the corresponding natural background elemental ratios. This contribution evaluated the detection and quantification of Ag, CeO_2, and Fe_2O_3 ENMs spiked in synthetic soft, or in natural river waters using the elemental ratio approach, and evaluated the effect of extractants including sodium hydroxide (NaOH), sodium oxalate (Na_2C_2O_4) and sodium pyrophosphate (Na_4P_2O_7) on the recovery of ENMs from the spiked waters. The extracted ENM concentrations were higher in Na_4P_2O_7-extracted suspensions than in NaOH- and Na_2C_2O_4-extracted suspensions due to the higher efficiency of Na_4P_2O_7 to break up natural and engineered nanomaterial heteroaggregates. The size distributions of the extracted suspensions were determined by asymmetrical flow-field flow fractionation coupled to inductively coupled plasma-mass spectrometer (AF4-1CP-MS). These size distribution analysis demonstrated that Ag ENMs were extracted from the spiked river water as both primary particles and small (<100 nm) aggregates, whereas CeO-2 ENMs were extracted from the spiked river water as aggregates of particles in the size range 0-200 nm The number particle size distribution of the extracted suspensions confirmed that Ag ENMs were extracted as a mixture of primary and aggregated Ag ENMs. Small Ag ENMs (ie. <20 nm) were detected by AF4-ICP-MS, but these particles were not detected by single particle (sp)-ICP-MS due to high size detection limit of sp-ICP-MS. This study illustrates that the elemental ratio approach is a promising approach to detect and quantify ENMs in surface waters. This study also illustrates the need for a multi-method approach, including extraction, filtration, AF4-1CP-MS and sp-ICP-MS, to detect, quantify, and characterize ENMs in surface waters.