Special Topic: Global Environment and Atmospheric Pollution
Air Pollution over Asia and the Influence of Biomass Burning
Atmosphere is a layer of gas surrounding our planet earth. Atmospheric component and its variation will have many effects on us in many ways. As problems of atmospheric pollutions are well recognized, in order to deal with the various environmental problems such as global warming and change in atmospheric composition, it is very important to study the current condition of the atmospheric pollutants emission and its effect. In this edition, we would like to introduce our recent research activities on the relation of air pollution and climate change.
Atmospheric Composition Research Program has participated in the observation campaign on the atmospheric chemistry in the Asia/Pacific Region conducted by NASA, and carried out model analysis on the variation of the ozone distribution. The current situation of the atmospheric pollution in the Asian region, which will have serious impacts not only on Japan, but also on the global environment, will be explained along with figures of model analysis.
Hajime Akimoto
Program Director, Atmospheric Composition Research Program
Frontier Research System for Global Change (FRSGC)


Air Pollution and Global Environmental Issues: Recent Trends

  The emissions of air pollutants in a broad sense caused by human activity is a prime cause of climate change and the variation in atmospheric composition. These are increasingly becoming important issue concerning the global environment. Therefore, in order to solve these issues, there is an urgent need to study the relationship between the current situation and factors affecting the emission of air pollutants. Figure 1 shows the trend of emissions of nitrogen oxide (NOx) by continent in the northern hemisphere (Akimoto, 2003). In Fig. 1, North America includes the US and Canada, Europe includes Russia and the Middle and Near East, and Asia includes East Asia, Southeast Asia, and South Asia. As shown in Fig. 1, the amounts of NOx emission over North America and Europe are approximately equal, and remained flat or slightly increased during the 1970s to 1980s; whereas in the 1990s,the emissions over Europe show a rapid decrease as a result of the strict regulation of NOx emissions in Western Europe. Meanwhile, although the amount of NOx emissions over Asia contributed little to the global total in 1970s, they subsequently rapidly increased to the point where they exceeded the amounts emitted in North America and Europe in the middle of the 1990s. It is predicted that this trend will continue over the next two decades, with emissions from Asia contributing more and more significantly in the first half of the 21st century. In order to deal with global warming, global environmental degradation, and other environmental issues, accurately assessing the impact from Asia due to emissions of not only NOx, but also carbon dioxide and aerosols is a key to deal with these countermeasures.



Fig. 1 Trend of anthropogenic NOx emissions over NorthAmerica, Europe, and Asia.

The Influence of Air Pollution over Asia in Recent Years

  There is a serious risk that increased emissions of air pollutants over Asia will strongly affect global climate change, the variation in atmospheric compositions over Asia, and the atmospheric environment in Japan. Figure 2 shows the variation of ozone distribution at ground level over East Asia, including Japan, in March 2001, simulated using the Regional Model (Zhang et al., 2003). At the same time, NASA in the US has carried out TRACE-P (TRAnsport and Chemical Evolution over the Pacific) atmospheric chemistry observations from aircraft over the Western Pacific. The Atmospheric Composition Group of the Frontier Research System for Global Change participated in this mission, and was in charge of model analysis.
  As shown in Fig. 2, made around the same time, there is a high concentration center of ozone in the Indochina Peninsula over Southeast Asia, with the high concentration zone of ozone extending out to Japan across South China.
   Air pollution caused by biomass burning (primarily from the burning of agricultural waste) is the main cause of the high concentration of ozone in the Indochina Peninsula. Air pollution caused by combustion of fossil fuels in South China generates more ozone. The last two days in Fig. 2 show a high-concentration plume of ozone reaching the southern part of Honshu, Japan, exceeding Japan's60 ppb Environmental Standard. This amount of ozone, over 75 ppb, is brought to Japan by long-range transportation. It is evident that such a situation will cause the reappearance of photochemical smog in Japan. The dark blue contours in Fig. 2 show the percentage of ozone derived from biomass burning, around 10 percent of which ultimately affects Japan. It is clear that the increased levels of air pollutants emitted over Asia, including not only China but also Southeast Asia, will bring a serious threat to Japan.

Fig. 2 Horizontal distribution of average ozone concentration near ground level, and the percentage of contribution from biomass burning (dark blue contours) in March 2001, evaluated by a model experiment.

Reference

Akimoto, H., Global air quality and pollution, Science, 302,1716-1719, 2003.

Zhang, M.-G., I. Uno, G.R. Carmichael, H. Akimoto, et al., Large-scale structure of trace gas and aerosol distribution over the western Pacific Ocean during the transport and chemical evolution over the pacific(TRACE-P) experiment, J. Geophys. Res., 108, D21,8820, doi: 10.1029/ 2002JD002946, 2003.
Frontier Newsletter/No.25
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