With the increase of consumption of fossil fuels, large amounts of pollutants released into the atmosphere cause serious health problems. Polycyclic aromatic hydrocarbons (PAHs) and nitropolycyclic aromatic hydrocarbons (NPAHs) are one of the atmospheric hazardous pollutants. The mutagenicities of several NPAHs are much stronger than those of PAHs, but the concentrations of NPAHs are much lower than those of PAHs in the environment. However, the progress of the study on the environmental behaviors and health effects of NPAHs have been much slower than that of PAHs, because of the lack of sensitive analytical methods for trace NPAHs. I developed a highly sensitive determination method for NPAHs by using HPLC with chemiluminescence detection. We organized an atmospheric PAHs and NPAHs monitoring network which covered East-Asian countries surrounding the Japan Sea (Japan, China, Korea and Russia) to collect air samples and applied the above method for the determination of PAHs and NPAHs. This review deals with analytical methods, behaviors and toxicities of PAHs and NPAHs in East Asia.

View full abstract

Aerial observations of atmospheric pollutants over the main land China and ground-based observations of long-range trans-boundary pollutants at a newly built observation site, CHAAMS (Cape Hedo Atmosphere and Aerosol Monitoring Station) were reviewed. Aerosols collected over the main land China were usually well neutralized contrary to our expectation. Sulfate exceeded ammonium in the western part but ammonium exceeded sulfate in the eastern part. It was speculated that the emission of ammonia gas in eastern China is much larger than SO₂ emission. Nitrate in aerosols was mainly contained in coarse particles at Cape Hedo, Okinawa. It was quite different from the situation observed in China, where most of nitrate was contained in fine particles. The most important reason for this is thermal instability of ammonium nitrate during the long-range transport. Ammonium nitrate formed in China as fine particles decomposed again to ammonia gas and nitric acid gas. Then, nitric acid gas must have deposited onto coarse particles such as sea salts and/or dust particles.

View full abstract

This study focuses on the performance of a Reynolds-averaged Navier-Stokes simulation (RANS) for air flow and gas dispersion in urban districts. The present numerical simulation is based on a finite volume method with an unstructured grid system to resolve the flow structure in a complex geometry. To evaluate the performance of RANS, the results are compared to those obtained by wind-tunnel experiments. The wind-tunnel experiments are conducted for gas dispersion from point sources in a complex residential area. The results show that RANS tends to underestimate the mean velocity and the turbulent intensities behind the relatively-high buildings. In addition, the mean concentration is strongly sensitive to the turbulent Schmidt number, which is the selective parameter appearing in the model of turbulent scalar fluxes, and RANS can be used to predict the concentration only when the optimum empirical value of the turbulent Schmidt number is selected.

View full abstract

The relationship between the composition of volatile organic compounds (VOC) and the high concentration phenomenon of a photochemical oxidant (O_x) in Saitama Prefecture was examined. Characteristics of the VOC composition depending on time and season were developed for the windward and leeward sites in Saitama. The high concentration components were alkanes and aromatics but the components with a high ozone formation potential were alkenes, aromatics and aldehydes. The main substances, which contribute to the ozone formation, were ethylene, propylene, butene, toluene, xylene, ethylbenzene, formaldehyde and acetaldehyde. Concerning the time variation, the VOC supply in the daytime seemed to be related to the high O_x concentration, and it was particularly suggested that the high VOC concentration in the prefecture's southern area in the daytime influenced the high O_x concentration in the northern area. In addition, the aldehyde concentration rose in the daytime in any season, especially in the summer. Also, the concentration variation was similar to O_x. It was shown that the photochemical reaction forms aldehydes, and it was considered that aldehydes strongly contribute to the O_x formation.

View full abstract

The 2011 Northeast Asian International Seminar on Air Quality Improvement was held in Seoul on Sep. 29, 2011, to improve the air quality in Northeast Asian cities and share ideas for future direction of policy and international cooperation.

View full abstract