Narrow Results

Fog water samples were collected at the Akita Hachimantai mountain range in northern Japan from August to September 1997 and from June to September 1988 to 2000 to investigate the pollution mechanism of fog. Ionic components and insoluble substances in fog water were analyzed using ion chromatography and particle induced X-ray emission (PIXE) analysis, respectively. Combining a 72 h back trajectory and principal component analysis (PCA) to chemical analysis data elucidated the effect of the transport course of an air mass on samples insoluble substances and ionic components. When the air mass was transported from northern China to the Hachimantai range, the nss-SO₄^2- was greater than in other cases. That fog contained "Kosa" as an insoluble substance from northern China. Our PCA analysis revealed that the score of PC1 (which was about –0.5) was a measure of containing "Kosa".

In order to shed light on the long-range transport of atmospheric pollutants in the Northeast Asian regions, we studied the chemical components in rime and fresh surface snow on Mt. Moriyoshi (altitude: 1454 m), located on the Sea of Japan side of northern Honshu, Japan, near Northwest China and Southwest Russia. Rime and fresh surface snow samples were collected at Juhyou-Daira (near the summit; altitude: 1200 m) in February 2004. The pH range of rime samples was 4.2 – 4.9, and the electric conductivity (EC) range was 52 – 282 μS/cm. On the other hand, the pH range of snow samples was 4.5 – 4.9, and the EC range was 17 – 77 μS/cm. The elemental compositions, ionic species and particle shapes of these samples were determined and/or observed by PIXE, ion chromatography and SEM-EDX analysis. PIXE analysis of the rime and snow samples revealed 24 elements, of which Na, Mg, Al, Si, K, Ca, Ti and Fe were found to be the major components. Comparing the determined values of rime and snow sample elements, rime samples were several times to several dozen times higher than snow samples for almost all the elements. For determined values of ionic species, rime samples were several times to several dozen times higher than snow samples. With the aid of SEM-EDX analysis, many small silicon-rich spherical particles were observed in the rime samples. Small silicon-rich spherical particles were also found in the snow samples. The existent forms of chemical components in rime will be an important factor when we consider the origin of air pollutants transported over long distances in the Northeast Asian regions.

The transport and chemical production processes of nitrate, sulfate, and ammonium aerosols over East Asia were investigated by use of the Models-3 Community Multi-scale Air Quality (CMAQ) modeling system coupled with the Regional Atmospheric Modeling System (RAMS). For the evaluation of the model's ability in depicting their 3-dimensional concentration distributions and temporal variations, modeled concentrations of nitrate, sulfate, and ammonium aerosols are compared with the observations obtained at a ground station in Japan in March 2001 and onboard of an aircraft DC-8 on 18 and 21 March 2001 during the Transport and Chemical Evolution over the Pacific (TRACE-P) field campaign. Comparison shows that simulated values of nitrate, sulfate, and ammonium aerosols are generally in good agreement with their observed data, and the model captures most important observed features, and reproduces temporal and spatial variations of nitrate, sulfate, and ammonium aerosol concentrations reasonably well, e.g., the timing and locations of the concentration spikes of nitrate, sulfate, and ammonium aerosols are well reproduced, but large discrepancies between observed and simulated values are also clearly seen at some points and some times due to the coarse grid resolution and uncertainties of the emissions used in this study. This comparison results indicate that CMAQ is able to simulate the distributions of nitrate, sulfate, and ammonium aerosols and their related species in the troposphere over East Asia reasonably well.