Abstract
The need to quantify engineered nanoparticles (ENPs) in the environment is due to the increasing incorporation of these particles in the daily products, which threatens human health and can possibly impact natural systems. Ceria NPs (CeO2NPs) and titanium dioxide NPs (TiO2NPs) are two of the most used ENPs in the world. In this study their occurrence was determined in river waters with accurate and relevant techniques such as single particle ICP-MS (spICPMS). In the Loire River (France), the variation of both CeO2NPs and TiO2NPs could be assessed locally, with an increase of the concentrations near a wastewater treatment plant (WWTP) outlet as well as in a lake connected to the river and dedicated to outdoor activities. In the upstream river water, supposedly less impacted by NPs, 6.4 ± 1.2 x 104 part mL-1 Ce-bearing and 13.4 ± 1.8 x 104 part mL-1 Ti-bearing particles were measured. These values increased to 33.9 ± 3.4 x 104 part mL-1 Ce-bearing and 80.3 ± 3.4 x 104 part mL-1 Ti-bearing particles near the WWTP outlet. Equivalent size for sphere distributions ranged from 24 nm to 70 nm for CeO2 and from 80 nm to 500 nm for TiO2 in the river water. In the lake, a raise of the concentrations has been observed with 38.3 ± 2.0 x 104 part mL-1 and 71.6 ± 2.1 x 104 part mL-1 containing Ce and Ti, respectively, with similar size distributions. FEG-SEM imaging confirms the occurrence of Ce- and Ti-bearing particles in the water samples. On the contrary, NPs seem to undergo strong heteroaggregation in the Loire river water. The Ce/La elemental ratios does not evolve from upstream to downstream the WWTP outlet, suggesting that a natural origin cannot be excluded to explain the increase observed in NPs number concentration. On the contrary, the Ce/La ratio increases in the outdoor activities center, which suggests the contribution of NPs potentially related to the cars parked nearby. Besides, elemental ratios Ti/V and Ti/Y have been assessed to highlight an anthropogenic source of Ti in both sampling sites, possibly to the sunscreens used during the summer.
Highlights
Engineered nanoparticles (ENPs) are of great importance thanks to their small size which gives them specific properties, especially valuable in different areas such as medicine (Zhang et al, 2008), biology (De et al, 2008), or industry (Piccinno et al, 2012)
The occurrence of CeO2NPs and TiO2NPs was determined with the use of single particle ICP-MS (spICPMS) and Field Emission Gun – Scanning Electron Microscopy (FEG-SEM) imaging at relevant environmental concentrations, displaying the NPs in the Loire River with different equivalent size for sphere distributions (CeO2: 24 nm to 70 nm; TiO2: 80 nm to 500 nm)
Near the wastewater treatment plant (WWTP) outlet, the occurrence of natural CeO2NPs was determined (Ce/La elemental ratio stayed constant) whereas in the outdoor activities center, CeO2NPs sources seemed to be anthropogenic since Ce/La elemental ratios increased, due to the cars in the parking lot
Summary
Engineered nanoparticles (ENPs) are of great importance thanks to their small size which gives them specific properties, especially valuable in different areas such as medicine (Zhang et al, 2008), biology (De et al, 2008), or industry (Piccinno et al, 2012). CeO2NPs are mostly selected for their high oxygen storage capacity (Zhang et al, 2011), their ability to absorb UV (Lima et al, 2009) and their low redox potential (Ce3+/Ce4+; Van Hoecke et al, 2009). They have several applications, especially in the automobile industry as a diesel fuel additive and as part of catalytic converters. Because of their anti-inflammatory properties (Hirst et al, 2009), these ENPs are useful in medicine. That is why the use of trustworthy analytical tools allowing the detection and quantification of ENPs in the environment, at relevant concentrations, is required
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