報告書番号

U99035

タイトル（和文）

9種の針葉樹と5種の落葉広葉樹の生長におよぼす人工酸性ミストとオゾンの単独および複合影響

タイトル（英文）

Effects of simulated acid mist and/or ambient ozone on the growth of nine coniferous and five deciduous broad-leaved tree species

概要 （図表や脚注は「報告書全文」に掲載しております）

我孫子研究所と赤城試験センターのオ－プントップチャンバ－を用いて，2年半にわたって，オゾンを除去した大気と除去しない現状大気のもとで14樹種を生育させ，同時に酸性霧の酸組成を模擬したpH5.0とpH3.0の酸性ミストを暴露し，生長への影響を調べた。その結果， 供試したほとんどの樹種において，pH 3.0ミスト区の生長はpH 5.0ミスト区に比べて増加した。このことから，pH3程度の酸性霧が樹木におよぼす直接影響は小さいと考えられた。一方，一部の樹種を除き，供試樹木の生長はオゾン処理によって低下し，現状レベルのオゾンでも樹木の生長への影響が懸念されることが明らかとなった。複合影響についてみると，一部の樹種ではオゾン処理による生長低下の程度はpH 3.0のミスト処理によって大きくなった。これは，酸性霧の硝酸分が葉に直接負荷されることによってオゾン影響を増大させる可能性のあることを示唆している。

概要 （英文）

Effects of simulated acid mist (pH 5.0/3.0, simulated the acid composition of highly acidic fog: 1:2:1 equivalent mixture of sulfate, nitrate and chloride) and/or ambient ozone (filtered air with/without activated-charcoals [CF/NF]) were tested using tunnel-type open-top chambers on the growth of young trees of nine conifererous and five deciduous broad-leaved tree species. Experiments were carried out at two sites of different altitude in Kanto district: Abiko Research Laboratory (25 m a.s.l.) and Akagi testing center (540 m a.s.l.). Parameters of dry weight growth for all tree species were assessed over experimental period of three seasons (from June in 1993 to November in 1995). Any visible foliar injury by the treatment of acid mist and ozone could not be found on all tree species. Total plant dry weights (TDWs) of Japanese red pine, Japanese black pine, Japanese larch, Japanese fir, Japanese cypress, Japanese cedar, poplar (Doronoki), Japanese white birch, Siebold's beech and Japanese zelkova were significantly increased in the mist treatment of pH 3.0 as compared with the treatment of pH 5.0. It was reported that a few percent of fogwater samples collected at the mountainous sites in Japan were at or below 3 of pH. These suggest that the acid fog observed in Japan could not induce any direct adverse effect on the trees. Significant reductions in TDW in the NF treatments were observed in red pine, larch, Japanese fir, Veitchi's silver fir, poplar, birch, beech and zelkova as compared with the CF treatment. Though no reductions in TDW could be seen, root dry weights of Norway spruce, Nikko fir and cedar were reduced in the NF treatments versus the CF treatments. Growth parameters of black pine, cypress and oak (Mizunara) were hardly affected by the ozone treatment. These results indicate that current ambient ozone may have adverse effects on the tree growth, except a few examined species, without visible foliar injury. Significant interactive effects of acid mist and ozone treatment were observed in TDWs of silver fir, poplar, beech and zelkova. The relative reductions in TDW of the NF-trees to the CF-trees at the mist treatment of pH 3.0 were greater than those at the mist treatment of pH 5.0. It was reported that ozone effects exacerbated by simulated acid rain of pH 3.0 may be due to the input of nitrate from the rain in the experiments investigating the combined effect of ozone and simulated acid rain on the growth of some Japanese trees. These results suggest that adverse effects of ozone on the growth of trees can be exacerbated, probably associated with nitrate, by the deposition of highly acidic fog on foliage or shoot.

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