June 25, 2004
The Ministry of the Environment issued a comprehensive report on the survey of acid deposition conducted from 1983 to 2002. This report was compiled by the Committee for Acid Deposition Measures from the results of the 1st to 4th Acid Deposition Surveys and the surveys in FY 2001 and 2002. Major findings of these surveys are:
| - | Acid precipitation equivalent to Europe and North America was observed nationwide, and inflow of contaminants deriving from the continent was seen on the coastline of the Japan Sea. |
| - | Currently, there seems to be no damages on ecosystem by acid deposition such as deterioration of vegetation or soil acidification. |
| - | In soil surrounding and rivers flowing into Ijirako (Lake Ijira), Gifu Prefectures, physical and chemical changes which may be caused by impacts from acid deposition, such as declining pH value, were observed. These changes are not so substantial to give immediate impacts on human health or vegetation and aquatic organisms in the surrounding area. |
<Outline of the report>
| 1. | Status of acid deposition (monitoring results of precipitation) Precipitation under pH 3, which may cause acute damages on plants, was not observed. On the other hand, according to the survey on FY 2000 to FY 2002, 5% of samples from 23 monitoring spots recorded under pH 4. This shows that precipitation in Japan is equivalent to that of European and North American countries. Seasonal variation of deposition of sulfate ions and nitric ions was observed. In the central north of the Japan Sea coastline in Honshu (Japan's main island) and San-in area, the deposition peaked in winter. In these areas, regions along the Japan Sea, it is presumed that the supply of oxides, like sulfur and nitrogen, to the atmosphere increases during winter. This indicates inflow of contaminants from the continent. A nation-wide increase of ozone concentration was seen in spring. The equivalent high concentration was observed along the coast of the Japan Sea, suggesting considerable influence by the transboundary air pollution. |
| 2. | Impacts on the ecosystem (monitoring results of vegetation, soil, and inland water) Currently, wide-ranging deterioration of vegetation caused by acid deposition is not recognized, therefore it was difficult to conclude that damages on the ecosystem by acid deposition were apparent. In the regions where vegetation monitoring was conducted, presumed causes of many of tree decline are disease and noxious insects (Bursaphelenchus Xylophilus, etc.). No tree decline with major causal factors deriving from acid deposition or soil acidification was detected. Generally, no drastic progress of soil acidification was observed. Exception was found in rivers and soil in the catchment area of Lake Ijira, where physical and chemical changes such as decreasing pH value which suggests impacts from acid deposition. These changes are not so substantial to give immediate effects on human health or vegetation and aquatic organisms in the surrounding area, but it is essential to have continuous and selective monitoring of the area and to have close observation on changes. |
| 3. | Future issues Adverse impacts of acid deposition can not be detected unless long-term monitoring was conducted continuously. When buffering capacity of soil or lakes and marshes are low, drastic impacts may be generated by accumulating a specific volume of acid substances. In this sense, steady implementation of long-term monitoring is essential. It is important to support monitoring activities and planning countermeasures in East Asian countries through the Acid Deposition Monitoring Network in East Asia (EANET) by promoting monitoring, survey and research, extensively. An integrated monitoring system which simultaneously correlates all environmental elements such as atmosphere, vegetation, soil, fresh water is essential. Selective monitoring is required for a catchment basin where impacts from acid deposition are suggested, such as Lake Ijira. Subjects for future research are; (i) analyzing mechanism of acid deposition impacts on ecosystem, (ii) analyzing mechanism of long distance transportation of air pollutants, and (iii) developing a comprehensive assessment model for issues on acid deposition in East Asian region. |