Characterization of chemical components of fresh and aged aerosol from vehicle exhaust emissions in Hong Kong.

The chemical properties of fresh and aged aerosol emitted during controlled vehicular exhaust emissions were characterized in the analysis. Pyrene (10417.1 ± 534.9 ng kg-1) is the most abundant of all analyzed compounds in total fresh emission and succinic acid (57359.8 ± 4000.3 ng kg-1) is for the total aged emission. The fresh emission factors (EFfresh) of all compounds in the n-alkanes group demonstrate higher average emissions for the two vehicles with EURO 3 standard compared to the other vehicles. The EFfresh for benzo [a]pyrene is in descending order: G1 (183.1 ± 144.7 ng kg-1) > G3 (103.4 ± 60.1 ng kg-1) > G4 (91.2 ± 80.1 ng kg-1) > G2 (88.6 ± 93.9 ng kg-1). Aged/fresh (A/F) emission ratios (>20) confirmed that these diacid compounds are generated by the photooxidation of primary pollutants that emitted from gasoline combustions. High A/F ratios (>200) in phthalic acid, isophthalic acid and terephthalic acid under idling mode imply relatively more intense photochemical reactions for their productions compared with other chemical groups. Strong positive correlations (r > 0.6) were observed between the degradation of toluene and formations of pinonic acid, succinic acid, adipic acid, terephthalic acid, glutaric acid and citramalic acid after the aging process, suggesting possible photooxidation of toluene that can lead to secondary organic aerosol (SOA) formation in the urban atmosphere. The findings demonstrate that vehicle emission standards for pollution in relation to the change of particulate matter chemical compositions and SOA formations. The results warrant a need for regulated reformulation for such vehicles.

Toxicological effects of fresh and aged gasoline exhaust particles in Hong Kong.

Exhaust emissions from gasoline vehicles are one of the major contributors to aerosol particles observed in urban areas. It is well-known that these tiny particles are associated with air pollution, climate forcing, and adverse health effects. However, their toxicity and bioreactivity after atmospheric ageing are less constrained. The aim of the present study was to investigate the chemical and toxicological properties of fresh and aged particulate matter samples derived from gasoline exhaust emissions. Chemical analyses showed that both fresh and aged PM samples were rich in organic carbon, and the dominating chemical species were n-alkane and polycyclic aromatic hydrocarbons. Comparisons between fresh and aged samples revealed that the latter contained larger amounts of oxygenated compounds. In most cases, the bioreactivity induced by the aged PM samples was significantly higher than that induced by the fresh samples. Moderate to weak correlations were identified between chemical species and the levels of biomarkers in the fresh and aged PM samples. The results of the stepwise regression analysis suggested that n-alkane and alkenoic acid were major contributors to the increase in lactate dehydrogenase (LDH) levels in the fresh samples, while polycyclic aromatic hydrocarbons (PAHs) and monocarboxylic acid were the main factors responsible for such increase in the aged samples.

Chemical and toxicological characterization of particulate emissions from diesel vehicles.

This paper presents a detailed chemical and toxicological characterization of the diesel particulate matter (PM) emitted from diesel vehicles running on a chassis dynamometer under different driving conditions. Chemical analyses were performed to characterize the contents of organic carbon (OC), elemental carbon (EC), and 31 polycyclic aromatic hydrocarbons (PAHs) in the collected PM samples. The OC-EC analysis results revealed that PM emissions from diesel vehicles in this study were dominated by OC and that the emission of vehicles equipped with diesel particulate filters had high OC/EC ratios. The PAH analysis results revealed that 4- and 5-ring PAHs were the dominant PAHs in the OC fraction of the PM samples. Particle toxicity was evaluated through three toxicological markers in human A549 cells, namely (1) acellular 2,7-dichlorofluorescein (DCFH) for oxidative potential, (2) interleukin-6 (IL-6) for inflammation, and (3) glutathione (GSH) for antioxidation after exposure. Statistical analyses revealed that vehicle sizes have statistically significant effects on the concentrations of the markers. Correlation analysis between PAHs and toxicological markers revealed that significant correlations existed between specific compounds and markers. Our results can be used as a reference by policy makers to formulate emission control strategies and as a dataset for other modeling studies.