Aline Lefol Nani Guarieiro

Vehicle Emissions: What Will Change with Use of Biofuel?

In urban areas, large concentrations of chemical compounds are emitted into the atmosphere by industries, vehicles and other human activities. Nearly 3000 different compounds, mostly organic, resulting from human activity have been identified in the atmosphere. This com‐ plex mixture of pollutants can have impacts on health and the environment. Thus, the sys‐ tematic determination of air quality should be, for practical reasons, limited to a restricted number of pollutants, defined in terms of their importance and the human and material re‐ sources available to identify and measure them. Generally, pollutants chosen to serve as in‐ dicators of air quality are the currently regulated and universally occurring compounds: sulfur dioxide (SO2), particulate matter (PM), carbon monoxide (CO), ozone (O3) and nitro‐ gen oxides (NOx). They are chosen due to their frequency of occurrence and adverse effects on the environment. Thus, the effects of air pollution can be characterized by a deterioration of good quality environmental conditions and the exacerbation of existing problems, which can manifest themselves in health, population welfare, vegetation, fauna, and urban struc‐ tures. The attention of regulatory authorities and researchers must not only look to the standards of air quality. There are compounds that despite being unregulated deserve atten‐ tion because of the damage they cause to the environment and, especially, to human health.

Chemical reactivities of ambient air samples in three Southern California communities

The potential adverse health effects of PM2.5 (particulate matter with an aerodynamic diameter <2.5 μm) and vapor samples from three communities that neighbor railyards, Commerce (CM), Long Beach (LB), and San Bernardino (SB), were assessed by determination of chemical reactivities attributed to the induction of oxidative stress by air pollutants. The assays used were dithiothreitol (DTT)- and dihydrobenzoic acid (DHBA)-based procedures for prooxidant content and a glyceraldehyde-3-phosphate dehydrogenase (GAPDH) assay for electrophiles. Prooxidants and electrophiles have been proposed as the reactive chemical species responsible for the induction of oxidative stress by air pollution mixtures. The PM2.5 samples from CM and LB sites showed seasonal differences in reactivities, with higher levels in the winter, whereas the SB sample differences were reversed. The reactivities in the vapor samples were all very similar, except for the summer SB samples, which contained higher levels of both prooxidants and electrophiles. The results suggest that the observed reactivities reflect general geographical differences rather than direct effects of the railyards. Distributional differences in reactivities were also observed, with PM2.5 fractions containing most of the prooxidants (74–81%) and the vapor phase most of the electrophiles (82–96%). The high levels of the vapor-phase electrophiles and their potential for adverse biological effects point out the importance of the vapor phase in assessing the potential health effects of ambient air. Implications: PM2.5 and its corresponding vapor phase, containing semivolatile organics, were collected in three communities in the Los Angeles Basin and examined with toxicologically relevant chemical assays. The PM2.5 phase contained most of the prooxidants and the vapor phase contained most of the electrophiles, whose content was highest in summer samples from a receptor site that reflected greater photochemical processing of the air parcel during its transport. As electrophiles initiate both adverse and adaptive responses to foreign substances by biological systems, their presence in the vapor phase emphasizes the importance of this phase in the overall health effects of ambient air.

Impact of the Biofuels Burning on Particle Emissions from the Vehicular Exhaust

In the last years, the use of alternative fuels has been shown to reduce emissions without negative effects on engine performance. There are also some studies that demonstrate an increase in particle emission with the use of biofuels. However, the literature reviewed here found noticeable decrease in particle emissions and smoke opacity with the use of biofuels. Indeed, many studies have been conducted to characterize and better understand biofuel proprieties related to particle emission.

In vitro Evaluation of Oxidative Stress Caused by Fine Particles (PM2.5) Exhausted from Heavy-Duty Vehicles Using Diesel/Biodiesel Blends under Real World Conditions

In this work, the redox activity of fine diesel/biodiesel particulate matter (PM2.5) was studied in order to approach its toxicity from reactive oxygen species, due to adverse effects it may cause to human health. The oxidative potential was measured by the dithiothreitol (DTT) assay in order to study the relative contribution of water-soluble transition metals, polycyclic aromatic compounds (PAH), nitro-PAH, and quinones. It was analyzed a total of 24 samples collected from primarily diesel/biodiesel-exhausted particles from buses. The rate concentrations of PM2.5 redox activity ranged 0.020-0.069 nmol min μg, with median at 0.040 nmol min μg (on average, 0.042 ± 0.005 nmol min μg for morning, 0.033 ± 0.007 nmol min μg for afternoon and 0.045 ± 0.009 nmol min μg for night). The transition metals appear to dominate the DTT response, since they were responsible up to 89% of redox activity measured in the samples. Apparently, the metal fraction contained in PM2.5 demonstrated a greater ability to catalyze reactions that promote the formation of reactive oxygen species when compared to organic compounds. It was observed that the oxidative potential of PM2.5 particles emitted from diesel/biodiesel (B7) is similar to diesel-emitted particles.

An Investigation on Morphology and Fractal Dimension of Diesel and Diesel‑Biodiesel Soot Agglomerates

INCT em Energia e Ambiente, UFBA, 40170-290 Salvador-BA, Brazil Department of Environmental Health Safety, University of California, Los Angeles-CA, USA Aerosol Dynamics, Inc., 935 Grayson St. Berkeley, 94710 Berkeley-CA, USA Instituto de Química, Universidade Federal da Bahia, 40170-290 Salvador-BA, Brazil Centro Interdisciplinar em Energia e Ambiente (CIEnAm), Universidade Federal da Bahia, 40110-040 Salvador-BA, Brazil