報告書番号

U02021

タイトル（和文）

常緑広葉樹におよぼす二酸化硫黄とオゾンの単独および複合影響

タイトル（英文）

Effects of sulfur dioxide and/or ozone on Japanese evergreen 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）

9種の常緑広葉樹をSO2とO3に17ヶ月間にわたり単独および複合で暴露し，生長や葉の可視害発現への影響を調査，解析した。その結果，シラカシ・クスノキ・マサキ・ネズミモチ・サンゴジュで20ppb SO2の暴露による生長等への影響が認められ，シラカシは10ppb暴露によっても影響がみられた。一方，ネズミモチ以外の8種では1.5倍O3の単独暴露による影響が認められ，そのうちのスダジイ・クスノキ・シャリンバイ・マサキ・サンゴジュでは1.0倍暴露によっても影響がみられた。また，スダジイではO3濃度が高いと20 ppb SO2による生長抑制の程度が増大した。したがって，現状のSO2濃度では一部の樹種以外は常緑広葉樹におよぼす単独影響およびO3との複合影響は極めて小さいと考えられる。一方，現状のO3の濃度は高感受性の常緑広葉樹への単独影響が懸念されるレベルにある。

概要 （英文）

Effects of sulfur dioxide and/or ozone were investigated using the open-top chambers on nine evergreen broad-leaved tree species. The experimental design was three levels of SO2 (filtered air with activated-charcoals [FA], FA added at a constant concentration of 10 or 20 ppb [24 hour/day ]) by two levels of O3 (FA, FA added in proportion to 1.0 times the ambient air [AA] in O3 [24 hour/day ]) plus ozone treatment of elevated concentration (FA added in proportion to 1.5 times AA in O3) at the lowest SO2 concentration for a total of seven treatments. Exposure to pollutants was conducted for two growing seasons (from August in 2000 to December in 2001) at the Akagi Testing Center of CRIEPI on the south slope of Mt. Akagi, Gunma Prefecture. Significant acceleration in leaf shedding resulting from exposure to SO2 at 20 ppb were restricted to Q.mysinaefolia. Any visible foliar injury by the SO2 treatment could not be found on all tree species examined in this study. Significant reductions in stem diameter increment and/or biomass resulting from exposure to 20 ppb SO2 were observed in five of the evergreen broad-leaved tree species (Q.mysinaefolia, Cinnamomum, Euonymus, Ligustrum and Viburnum), as compared with the FA treatment. Q.mysinaefoli also reduced biomass at 10 ppb SO2 treatment. The O3 treatment at 1.5 times AA accelerated the leaf discoloration and/or shedding in all tree species examined except Ligustrum , as compared with the FA treatment. The leaf shedding in five of the evergreen broad-leaved tree species (Castanopsis, Cinnamomum, Rhaphiolepis, Euonymus and Viburnum) was also accelerated at 1.0 times O3 treatment. The O3 treatment at 1.5 times AA significantly reduced stem diameter increment and/or biomass of six evergreen broad-leaved tree species (Q.mysinaefolia, Castanopsis, Cinnamomum, Rhaphiolepis, Euonymus and Viburnum) as compared with the FA treatment. Euonymus showed further reduction of biomass at the 1.0x O3 treatment. Though no reduction in biomass could be induced by either SO2 at 20 ppb or O3 at 1.0 times AA alone, the combination of both pollutants synergistically reduced biomass of Castanopsis. These results indicated that (i) the current ambient concentration of SO2 in Japan (5 ppb for 24 hour mean) or in combination with ambient O3 is low for inducing the adverse effect on all tree species, (ii) the current ambient level of O3 or highest concentration of SO2 (10 ppb for 24 hour mean) in Japan is high enough to have adverse effects on the evergreen broad-leaved tree species sensitive to O3 or SO2 respectively, (iii) the synergistically interaction between SO2 and O3 at the current ambient level is unlikely to be found on the growth of evergreen broad-leaved tree species examined in this study.

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