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

Abstract

ABSTRACT:Nanoceria (i.e., CeO 2 nanoparticles) fuel additives have been used in Europe and elsewhere to improve fuel efficiency. Previously we have shown that the use of a commercial fuel additive Envirox TM in a diesel-powered electricity generator reduced emissions of diesel exhaust particle (DEP) mass and other pollutants. However, such additives are currently not permitted for use in on-road vehicles in North America, largely due to limited data on the potential health impact. In this study, we characterized a variety of physicochemical properties of DEPs emitted from the same engine. Our methods include novel techniques such as Raman spectrometry for analyzing particle surface structure and an assay for DEP oxidative potential. Results show that with increasing Envirox TM concentrations in the fuel (0x, 0.1x, 1x, and 10x of manufacturer recommended 0.5 ml Envirox TM per liter fuel), DEP sizes decreased from 194.6±20.1 to 116.3±14.8 nm; zeta potential changed from -28.4 mV to -22.65 mV; DEP carbon content decreased from 91.8% to 79.4%; cerium and nitrogen contents increased from 0.3% to 6.5% and 0.2% to 0.6%, respectively; the ratio of organic carbon (OC) to elemental carbon (EC) increased from 22.9% to 38.7%; and the ratio of disordered carbon structure to ordered carbon structure (graphitized carbon) in DEP decreased. Compared to DEPs emitted from 0x, 0.1x, and 1x fuels, DEPs from the 10x fuel had a lower oxidative potential likely due to increased ceria content because pure ceria nanoparticles exhibited the lowest oxidative potential compared to all the DEPs. Since the physicochemical parameters tested here are among the determinants of particle toxicity, our findings imply that adding ceria nanoparticles into diesel may alter the toxicity of DEPs. The findings from the present study, hence, can help future studies that will examine the impact of nanoceria additives on DEP toxicities.

Uptake of Cerium Dioxide Nanoparticles and Impact on Viability, Differentiation and Functions of Primary Trophoblast Cells from Human Placenta

“…Today, the novel CeO 2 NPs are found in our everyday lives in several consumer products [ 7 ], but pregnant women are mainly exposed to CeO 2 from air pollution [ 47 , 48 ]. Thus, most of the studies on CeO 2 NP toxicity have focused on cellular models like the lung [ 49 , 50 , 51 , 52 , 53 ], and their effects during the narrow period of human pregnancy, and particularly on the human placenta, are poorly understood.…”

Effects of Nonthermal Plasma on Microstructure and Oxidation Characteristics of Particulate Matter

“…The spectral parameters of several bands, especially the D1 band at 1350 cm –1 , exhibit a pronounced dependence on the excitation laser wavelength and allow distinguishing different sample materials. Peak fitting provides the parameters of the peak position, FWHM, intensity, and area integral of each peak. − Analyzing these parameters enables exploring the variation in a crystal structure during PM oxidation by NTP.…”

Advancing the Understanding of Environmental Transformations, Bioavailability and Effects of Nanomaterials, an International US Environmental Protection Agency—UK Environmental Nanoscience Initiative Joint Program

“…Modeling studies suggest the nano-ceria additive has the potential to reduce the overall ambient DEPs concentration in many regions of the US (Figure 2). The addition of nano-ceria also affected several physicochemical properties of DEPs (e.g., reducing particle size, reducing carbon content, increasing cerium content, increasing organic carbon to elemental carbon ratio, and reducing oxidation potential) [69] [70]. These transformations may be responsible for the changes in bioreactivity and reduction of DEPs toxicity observed in several experiments conducted with cultured human lung cells, mice cells and zebrafish embryos.…”