Fate of engineered cerium oxide nanoparticles in an aquatic environment and their toxicity toward 14 ciliated protist species

Abstract

The potential environmental impacts of engineered cerium oxide nanoparticles (CeO2 NPs) on aquatic organisms have remained largely unknown. Therefore, the laboratory study featured herein was performed to determine the fate of CeO2 NPs in an aquatic environment and their toxicity towards 14 different ciliated protist species at a specified population level. An investigation of 48 h aggregation kinetics in the Dryl's solution showed the CeO2 NPs to be relatively stable. The pH values in three test medium were too far away from PZC, which explained the stability of CeO2 NPs. CeO2 NPs generally elicited more toxicity with increasing NP concentration, following certain dose-response relationships. Nano-CeO2 resulted in greater toxicity in a particle state than when added as bulk material. LC50 values showed a negative correlation with the surface-to-volume ratio for these protists, suggesting that surface adsorption of CeO2 NPs might contribute to the observed toxicity. Additionally, acute toxic responses of 14 ciliated protist species to CeO2 NPs were not significantly phylogenetically conserved. The results of these observations provide a better insight into the potential risks of CeO2 NPs in an aquatic environment.

Behavior and Potential Impacts of Metal-Based Engineered Nanoparticles in Aquatic Environments

“…Moreover, the acute toxicity of metal oxide NPs to Paramecium multimicronucleatum has shown that the 48-h LC 50 values of these NPs decreased as follows: Al 2 O 3 < TiO 2 < CeO 2 < ZnO < SiO 2 < CuO < Fe 2 O 3 NPs ( Figure 3 a), suggesting a positive correlation between the bonding strength of metal oxide NPs and the cell surface and the toxicity in unicellular organisms ( Figure 3 b,c) [ 212 ]. Furthermore, a recent study on the toxicity of CeO 2 NPs to 14 ciliated protist species showed that the CeO 2 NP adsorption on the protist surface rather than phylogenetical conservation induced the toxicity due to a negative correlation between LC 50 values and the surface-to-volume ratio of protists [ 213 ]. In addition, based on the chronic exposure to 1 and 5 mg·L −1 of TiO 2 NPs for 21 days, severe growth retardation, mortality and reproductive capacity reduction were all observed in D. magna .…”

“… Surface interactions affect the toxicity of metal oxide NPs toward Paramecium : ( a ) survival ratios of P. multimicronucleatum after 48 h of exposure to NPs; ( b ) net interaction energy profiles between NPs and P. multimicronucleatum ; ( c ) relationship of the magnitude of energy barrier and the 48-h LC 50 of metal oxide NPs to P. multimicronucleatum (reproduced with permission from [ 213 ], Copyright American Chemical Society, 2012) …”

Distribution, Bioaccumulation, Trophic Transfer, and Influences of CeO2 Nanoparticles in a Constructed Aquatic Food Web

“…27 The size and surface modifications of CeO 2 NPs obviously influenced the temporal partition behavior of nanoparticles in aquatic systems and their bioavailability and toxicity to the biota species. 22,23,25 Nevertheless, previous studies on food chains containing no more than three species could not fully represent the situation of a complete ecosystem or mimic the real environmental scenario. It was thus of importance to study the long-term effect of CeO 2 NP exposure in a water ecosystem constituted by multiple abiotic and biotic components to clarify their environmental fate and potential impacts.…”

“…27 The size and surface modifications of CeO 2 NPs obviously influenced the temporal partition behavior of nanoparticles in aquatic systems and their bioavailability and toxicity to the biota species. 22,23,25 Nevertheless, previous studies on food chains containing no more than three species could not fully represent the situation of a complete ecosystem or mimic the real environmental scenario.…”

The applications of cerium oxide nanoform and its ecotoxicity in the aquatic environment: an updated insight

“…Nanoparticles (NPs) are unparalleled compounds due to their tiny size ( than 100 nm), and size-dependent characteristics (length, width, height, volume, and mass) (Zhang et al, 2016). Currently, the production of engineered NPs, especially metal oxide nanomaterials (NMs) were extensively increased due to the numerous and widely used commercial applications worldwide.…”