中国山地に降る酸性雨の分析

More than 30 years ago, the pine trees in the mountain-side of the Chugoku district in Japan, started to die. Since then, a lot of pine trees have continued to die, and the damage area was spreading out even now. It is considered that one of the reason on the death of the pine trees might be "the acid rain" falling in the district. The rains and the underground water at Daikinya, Kuse-cho, Maniwa-gun, Okayama Pref. in the district were analyzed chemically by Funatsu in 1995-1997; the conductivity, the density of nitric ion (N0(3)(-)) and sulfuric ion (SO(4)(2-)), and the acidity (pH) in the rains were thus observed. In the present paper the results of the analysis on the rains have been reported. (1) The conductivity varied 4.2-197.0 μs/cm, and the average was 39.0. (2) The density of nitric ion (NO(3)(-)) varied 1.6-84.2 ppm, and the average was 22.4. (3) The acidity (pH) varied 3.7-7.5, and the average was 4.9. The acid rains falling continuously in this district in the past two years were confirmed.

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