Sensitivity of East Asian Ecosystem to Acid Deposition

Sensitivity of East Asian ecosystem to acid deposition 

There is agreement both nationally and internationally that long-range transboundary air pollution may span continents pollutants are transferred from Europe to North America and Asia as well as in the opposite directions (Sofiev, 1998). Consequently, the calculation and mapping of critical loads as indicators of ecosystem sensitivity 

The applicability of these approaches for the assessment of acidification loading on the terrestrial ecosystems in Asia is made here using the examples of Asian domain (Asian part of Russia, China, Japan, Taiwan, Korea and Thailand). In spite of the great differences in climate, soil and vegetation conditions, these regions can serve as a good test of the proposed methodology. 

As regards the pollutants monitoring, from the measurements available so far it could be concluded that acid rain is coming to be a major problem in Asia. In many industrially developed and new developed countries such as Japan, China, Taiwan, South Korea, Thailand etc the values of pH 5 are encountered at many sites, and they represent more than 50% of monitored rain events on a regional scale. In some developing countries of South-East Asia (Myanmar, Laos, Cambodia) most rainwater pH measurements tend to be around 5.6, the pH of natural rainwater and the acid rain precipitation are mainly due to localized industrial pollution. There is some evidence that pH values below 5 at unpolluted sites may be due to the contribution of weak organic acids, such as formic and acetic acids (Radojevic 1998). 

The influence of acid rain on the environment is related to the various properties of different ecosystems and varies depending upon physic-chemical characteristics of soil, vegetation type, stemflow and throughfall interactions of rainwater with canopy of different botanic species. For instance, it is well known in Japan that soils close to the stems of Japanese cedar (Cryptomeria japonica) trees are strongly acidic. This is partly due to the leaching of hydrogen ions from the stems. Soil solutions close to a stem (10cm) are markedly acidic (pH 4.5) and contain 47 /zM of total Al in 

---