Factors Affecting the Ambient Physicochemical Properties of Cerium-Containing Particles Generated by Nanoparticle Diesel Fuel Additive Use

Abstract

Despite the use of cerium oxide nanoparticles (nCe) in some regions as a diesel fuel additive, the physicochemical properties of the resulting exhaust particles in the ambient atmosphere are not well known. The mixing state of ceria with other exhaust particles is one such physicochemical property that has been shown to potentially affect ecosystem/human health. In this study, ceriumcontaining particles associated with an nCe additive were collected in the laboratory and in Newcastle-upon-Tyne, UK where the local bus fleet uses the Envirox nCe additive. Electron microscopy of laboratory-generated exhaust samples indicated both individual ceria and soot particles (external mixture) and ceria contained within soot agglomerations (internal mixture). Low ambient concentrations prevented quantification of the ceria particle mixing state in the atmosphere; therefore, a multicomponent sectional aerosol dynamic model was used to predict the size, chemical composition, and mixing state of ceria particles as a function of distance from an idealized roadway. Model simulations predicted that most ceria particles remain nonmixed in the ambient atmosphere (300 m downwind from the roadway) due to slow coagulation, with the mixing rate most sensitive to the ceria content of emitted nuclei-mode particles and the particle concentration upwind of the road. Although microscopy analysis showed both external and internal mixtures of ceria and soot in freshly emitted particles, the ambient mass concentration, and size distribution of ceria particles predicted by the model was insensitive to the emitted mixing state.

Treatment of Human Lens Epithelium with High Levels of Nanoceria Leads to Reactive Oxygen Species Mediated Apoptosis

“…These properties arise from the ability of cerium ions to co-exist and transition between trivalent and tetravalent oxidation states (Ce 3+ , Ce 4+ ) at the surface defects present in the CeO 2 crystalline structure allowing nanoceria to release or acquire oxygen depending on the ambient environment [9,10]. Additionally, nanoceria are increasingly used for industrial applications such as an additive to diesel fuel (commercially available under several trade names such as Envirox™) to reduce soot emissions and decrease fuel consumption [11,12]. This has led to increased exposure to nanoceria which warrants investigation of their toxicological effects and interactions with various eukaryotic cells.…”

Pulmonary toxicity of inhaled nano-sized cerium oxide aerosols in Sprague–Dawley rats

“…2008a, Gantt et al. 2015) and there are concerns about their potential impact on health following inhalation (Geraets et al. 2012).…”

Effects of a nanoceria fuel additive on the physicochemical properties of diesel exhaust particles

“…These physicochemical properties might be further altered after DEP is released into the environment, 12 which needs to be addressed in future studies. Given that these physicochemical properties are important determinants of particle toxicity, it is anticipated that using nanoceria additives to diesel fuel would alter the toxicity of the emitted DEP in various ways.…”

“…6,7,12 The chemical form of cerium may be an important determinant of particle toxicity, as suggested by a recent study reporting that cerium oxide (ceria) nanoparticles are more toxic than other form of cerium particles. 25 As shown in Figure 1, ceria in the DEP had a size of 100 to 200 nm, representing particle agglomerates rather than the single ceria particles of 5-10 nm originally added into the fuel.…”

“…25 As shown in Figure 1, ceria in the DEP had a size of 100 to 200 nm, representing particle agglomerates rather than the single ceria particles of 5-10 nm originally added into the fuel. 12 The larger size agglomerates are expected to be less toxic and bio-reactive than smaller non-agglomerated particles. Furthermore, TEM images showing the morphology of DEPs for three diesel fuels (0x, 1x and 10x) are presented in Figure 2.…”