In this article, our developed emission inventories of PAHs, REAS-POP and chemical transport model, RAQM2-POP, which cover Northeast Asian region, are introduced. Validities of RAQM2-POP and REAS-POP were confirmed by agreement with the other PAHs inventory in China and the observed PAHs concentrations in Northeast Asia. Simulated atmospheric concentration distributions of PAHs in Northeast Asia revealed that PAHs concentrations in Noto, Japan in winter were mainly dominated by biomass and coal combustion and coal transformation in China. On the other hand, those in summer were dominated by mobile sources in Japan. Our modeling study demonstrated importance of transboundary air pollution from the Asian continent in winter Japan. As for future issues, clarification of PAHs concentration distributions in Northeast Asia after recent emission controls from mobile and stationary sources in China will be necessary. Furthermore, atmospheric deposition distributions of PAHs and its impact on ecosystem in Northeast Asia should be elucidated.
Polycyclic aromatic hydrocarbons (PAHs), as well as inorganic gaseous pollutants such as sulfur oxides, have recently been observed with extremely high concentration in China. Increase of coal consumption in China would increase concentration of air pollutants, causing serious health problems. These pollutants are also transported from the Asian Continent to Japan in the same way as Asian dust. The present review is concerned mainly with the atmospheric transport of the hazardous PAHs and their derivatives from the Asian Continent to Japan. In addition, this review also deals with recent studies on atmospheric concentrations in China and related countries.
Secondary organic aerosol (SOA) accounts for a major mass fraction of aerosol that influences global climate and air quality. Although considerable progress has been made in the understanding of SOA formation processes, accurate prediction of SOA formation remains a major challenge due to the incompleteness in understanding major precursors of SOA and their reactions in the atmosphere. This review outlines recent studies on missing potential sources of SOA, especially intermediate volatility organic compounds (IVOC). Polycyclic Aromatic Hydrocarbons (PAH) have acquired increasing attention as a potentially important class of IVOC that contributes to SOA formation. Additionally, studies on SOA formation from alkane and phenolic compounds are reviewed as other significant classes of IVOC.
The heterogeneous reactions of atmospheric oxidants with aerosol particles are of central importance to air quality. Polycyclic aromatic hydrocarbons (PAHs) are efficiently oxygenated upon exposure to ozone, which leads to an enhancement in toxicity. For a wide range of substrates, including solid and liquid organic and inorganic substances, the concentration and time-dependence of the heterogeneous reaction between PAHs and O3 can be well described by a Langmuir-Hinshelwood mechanism. Competitive adsorption and chemical transformation of the surface lead to a strong non-linear dependence of uptake coefficient of O3 on time and gas phase composition, with different characteristics under dilute atmospheric and concentrated laboratory conditions. Long-lived reactive oxygen intermediates (ROIs) are formed upon decomposition of O3 on PAH surface. The ROIs reconcile apparent discrepancies between earlier quantum mechanical calculations and kinetic experiments. They play a key role in the chemical transformation and adverse health effects of toxic and allergenic air particulate matter. Moreover, ROIs may contribute to the coupling of atmospheric and biospheric multiphase processes.
Previous epidemiological studies have indicated that ambient particulate matter (PM) might be a risk factor for the development/exacerbation of respiratory and cardiovascular disease. One of the major sources of urban atmospheric PM is assumed to be diesel exhaust particles (DEP). Many experimental studies have demonstrated that ambient PM or DEP may enhance inflammatory responses mediated especially by organic chemical components including polycyclic aromatic hydrocarbons (PAHs). PAHs can induce reactive oxygen species (ROS) generation that leads to lipid peroxidation and DNA damage. Oxidative stress may be one of the responsible factors in the toxicological and inflammatory effects of chemicals. Recently, we have examined the differences in the effects of PAHs and their related chemicals on the respiratory cells and immune cells. We observed that oxidative stress, cytotoxicity, and inflammatory responses were induced by some chemicals such as compounds containing hydroxyl, carbonyl, or nitro groups. Taken together, the toxicological effects of PAHs and their derivatives may be related to their chemical structures such as functional group and isomer. These differences may lead to the different function such as intracellular metabolism, cell membrane permeability, and receptor binding not only oxidative stress.
Ventilation of air in a vehicle is one of the important characteristics to maintain the indoor air quality, and the ventilation performance changes depending on the driving and other conditions. The present study evaluated the ventilation performance through the continuous measurements of airborne particulate matters in a moving vehicle under various conditions including driving speed, flow rate of air from an air-conditioner, window opening, and particle emitting. Cigarettes were used as a source of particles. One cigarette was smoked at 7 puffs/min in a vehicle. Light scattering photometers were used for measuring the aerosol concentration at 10 s interval. Driving speed was kept constant at zero (stopping), low (20 km/h), medium (40 km/h) and high (100 km/h). The ventilation performance was evaluated by using the apparent air change rate and the decay rate of aerosol concentration in the vehicle. The aerosol concentration decay rate was the ratio of the concentration just after smoking (2.5 minute average) and the concentration during smoking (6.5 minute average). As a result, we found that the ventilation performance during the moving is much better than that during stopping, and the apparent air change rates changed 28.2-93.5 h-1 during moving and 9.5 h-1 during stopping and air-conditioner-off condition.
Airflow measurements in narrow space such as in boundary layer is important in order to study the relationship between the airflow turbulence and the aerosol behavior. However, the measurement is extremely difficult when the airflow speed is low. In this study, an evaluation technique of airflow turbulence by the measurement of pressure difference by a CMOS pressure gauge was proposed. The measurement of pressure difference was conducted using small tubes which are applicable to narrow space. The CMOS pressure gauge had a quick response to airflow turbulence at a high frequency. Preliminary test showed that the CMOS pressure gauge can provide airflow measurement with a high accuracy in wide range even at a very low airflow velocity. It was also found that the measurement accuracy was improved with an oversampling technique, even when the resolution of a sensor was not enough. The evaluation of airflow turbulence by CMOS pressure gauge had many advantages over the conventional measuring techniques.
PM2.5 samplings are difficult on a site where no electricity is available because almost all commercially available samplers are operated by AC100V. We developed a solar powered PM2.5 sampler consisting of solar panels, a charge/load controller, a battery, and a DC pump. PM2.5 concentrations obtained using the sampler agreed well with those measured by a continuous PM2.5 monitor utilizing a combination of beta attenuation and light scattering technology. We found that the pump should be stopped when the battery voltage is lower than a certain level in order to maintain the air flow rate during the sampling period. We simulated the remaining battery power taking into account the number of solar panels, the energy consumption of a pump, and other parameters. Several suggestions were made for the readers who may want to customize our device.