Organic compounds are ubiquitous in ambient aerosol and constitute a substantial fraction of total fine particle mass in anthropogenic air. Analytical techniques for measuring organic aerosols (both in terms of compound level and total mass) have not been fully established because organic aerosols consist of hundreds to thousands of chemical species with a very wide range of chemical and thermodynamic properties. This paper reviews some representative methods for the measurements of total mass concentrations of organic carbon (OC) and organic matter (OM) in ambient aerosol. The OC measurements include a thermal-optical reflectance/transmittance method and a particle-into-liquid sampling (PILS) method. The OM measurements include an Aerodyne aerosol mass spectrometer (AMS) and an off-line analysis by gravimetric mass measurements. The advantages and limitations of each method are discussed.
The sensitivity of thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) was greatly improved by replacing the thermal desorption unit and mass spectrometer and by applying the selected ion monitoring method. Quantification limits of 12 polycyclic aromatic hydrocarbons (PAHs) , 17α (H) , 21β (H) -hopane, and C18-C36n-alkanes were 4-17, 13, and 13-39 pg, respectively. For extremely small amount (≈ 20 μg) of standard reference materials (1649a, 1650b, and 2975) , PAH concentrations determined by TD-GC/MS agreed reasonably well with the certified values. TD-GC/MS was applied to size-resolved particles in diesel exhaust, and in roadside and background atmospheres. For diesel exhaust particles emitted under no-load condition, 17α (H) , 21β (H) -hopane concentrations per particle mass were higher in smaller particles, suggesting that lubricating oil was the major component of the nuclei-mode particles (particles with a modal diameter of 0.01-0.03 μm) . For the roadside and the background particles, 17α (H) , 21β (H) -hopane concentrations per particle mass were also higher in smaller particles after correction for evaporation of 17α (H) , 21β (H) -hopane in the atmosphere. The results suggest that nanoparticles (≤0.03 μm) in the roadside and the background atmospheres originated mainly from oil-rich nanoparticles in diesel exhaust, although a large proportion of their original components had evaporated.
Secondary organic aerosol, produced by the atmospheric oxidation of volatile organic compounds, comprises a substantial portion of the total mass of atmospheric fine aerosols, but its formation mechanisms are incompletely understood. In this feature article, paying the central attention to the isoprene oxidation, whose contribution to atmospheric fine aerosol has recently been suggested, I introduce the recent developments in understanding the secondary organic aerosol formation. The aims of this feature article are (1) to explain why isoprene is previously excluded from the possible aerosol precursors, (2) to introduce the recent developments, (3) to summarize the current knowledge and (4) to elucidate the possible problems that should be discussed in the future works.
An ambient particulate matter (PM) concentration prediction with air quality models requires detail emission inventory data of emitted PM composition data with respect to particle size for directly emitted PM. For organic and inorganic aerosol formation due to gas-to-particle conversion, VOCs (volatile organic compounds) speciation data are also needed. In this paper, Japanese PM and VOCs speciation data are listed as input data of aero4 module in CMAQ (Community Multiscale Air Quality) model. From the view point of PM prediction, present problems of Japanese emission inventory are also discussed.
Evidence has been accumulated to show that the particulate matter in polluted air is associated with increased cardiovascular morbidity and mortality. Our studies demonstrated that the effect of single intrataracheal instillation of PM2.5 in Spontaneous Hypertensive Rat (SHR) decreased the heart rate (HR) and increased the parasympathetic nervous activity. Five hours exposure to PM2.5 tended to enhance the lung resistance, leading to a decreased in HR and an increase in parasympathetic nervous activity. There were no significant changes in the sympathetic parameter. These results suggest that the cardiac function may play a role in pathogenesis relating to harmful effect of PM2.5 on SHR. More comparative study is needed for health effect of PM2.5, ultrafine particles and nanoparticles.
Beijing and Tokyo are both megacities. As the raw material ratios on the fundamental energy for each city function are different, the major sources of aerosols in each city must be different. In this study, we compared the compositions of carbonaceous materials and the ratios of stable carbon isotopes (δ13C) of soot in aerosols collected in both megacities. The ratio of organic carbon (OC) to elemental carbon (EC) in atmospheric aerosols in Beijing showed seasonal variation, whereas the OC/EC ratio showed little seasonal variation in Tokyo. The δ13C of the atmospheric aerosols in Beijing was -24.0 ± 0.3 ‰ in the heating period (November to March) reflecting the high contribution of particles derived from coal combustion, and its value was -25.1±0.6 ‰ in the non-heating period (April to October) when contributions from sources other than coal combustion increased. On the other hand, the δ13C of the atmospheric aerosols in Tokyo was approximately constant throughout the year at -25.1 ± 0.1 ‰. Because there are clear differences between the δ13C of the atmospheric aerosols in the winter and spring seasons in Beijing and Tokyo, we consider this to be a good index for examining long-range transport aerosols.
Direct injection- thermal desorption- gas chromatograph/mass spectrometry (DTD/GC/MS) is applied to fine particulate matter (PM) in environmental tobacco smoke (ETS) . In this method, PM collected on quartz fiber filter is directly put into an injector of GC, and desorbed organic gas is analyzed by GC/MS. Nicotine and 12 kinds of PAHs in PM of μg-level are determined within 30 minutes without any pretreatment. The determination limits for nicotine and BaP were 25 pg and 150 pg, respectively. Ultrafine particles in ETS of smoking and non-smoking area were analyzed. Nicotine and PAHs of low vapor pressure should be a marker of tobacco smoke. Carcinogenic Dibenzo (a, h) anthracene was detected only in the smoking area. Ultrafine particles in simulated ETS were also analyzed. Time course of each chemical in different size PM was obtained.
Test air filter media consisting of uniformly-packed fibers were prepared from water-dispersions of micro glass fibers with different diameters by hand making. Through the evaluation of collection performance of these filter media, it was found that the pressure drop of filter media prepared in this work was in good agreement with that of Fan Model Filters, showing that they were highly uniform in fiber packing. It was also experimentally shown that the filter media consisting of fibers with diameter smaller than 0.5 μm have a quality factor higher than those of coarser fibers. Furthermore, it was found that the difference between theoretically-predicted quality factors and the experimental ones is apt to be exaggerated when the particle penetration is high. These results are useful in designing the filter media for the energy-saving purpose, achieving low pressure drop and high collection efficiency at the same time.