Measurement of atmospheric aqueous phase OH radical and the elucidation of its toxic effects on higher plants

本文研究了大气水相羟基自由基的化学组成及其对高等植物生理状态的毒性效应。首次开发了自动、快速、灵敏地测定水相OH自由基的分析技术，并成功地应用于雨露样品的分析。对大气水相OH自由基来源的鉴定表明，硝酸盐、亚硝酸盐和Fenton反应(包括过氧化氢和溶解的铁物种)是雨、露水样品中OH自由基的主要来源，但未知的OH来源(有时高达50%)仍有待阐明。柴油车尾气鼓泡液中存在ppb水平的亚硝酸盐，产生的氢氧化氢为微米/小时，而汽油车几乎不产生氢氧化氢。我们的研究表明，大气水相中的OH自由基来源于产生OH的物质，包括硝酸(Nitrate)、亚硝酸根(…更多的酸(亚硝酸盐)、过氧化氢和存在于大气中的铁物种以及产生OH的重要人为来源之一可能是柴油尾气。羟基自由基生成液(光芬顿试剂)熏蒸红松幼苗2~3个月后，叶片水平的光合作用活性和气孔导度下降，个体水平的生物量下降。有趣的是，在暴露试验的熏蒸液中加入自由基清除剂甘露醇后，OH的影响大大减弱，从而有效地控制了OH对松树的毒性效应。此外，松树的生长模型表明，在每年的OH产生物质暴露下，松针的光合作用产量下降，导致生物量减少，最终导致树木死亡。一个数值模拟研究了广岛县不同人为来源的氮氧化物和二氧化硫的排放趋势。在该地区，钢铁等固定污染源是这些污染物的主要排放者。然而，随着节能降耗新技术的发展，从1990年到2010年，这些污染物的排放量将减少20%-30%。主要空气污染物排放量的减少将导致该县空气污染的显着改善，因此松林不太可能进一步下降。较少

Chemistry of atmospheric aqueous phase hydroxyl radical (OH radical) and its toxic effects on the physiological status of higher plants have been investigated in this study. Analytical technique for automatic, rapid and sensitive measurement of aqueous phase OH radical was firstly developed and it was successively applied to the analysis of rain and dew samples. Identifications of sources of atmospheric aqueous phase OH radical indicated that nitrate, nitrite and Fenton reaction (involving hydrogen peroxide and dissolved iron species) are major sources of OH radical in rain, dew samples whereas unknown sources of OH (sometimes up to 50%) remain to be elucidated. The ppb level of nitrite existed in bubbling solution of the exhaust gas of diesel cars produced uM/h of OH whereas almost no OH generated in that of gasoline cars. From our studies, it can be concluded that atmospheric aqueous phase OH radical is originated from OH producing substances including nitric acid (nitrate), nitrous … More acid (nitrite), hydrogen peroxide with iron species occurring in the atmosphere and one of important anthropogenic sources of OH producing substances may be diesel exhausts. Decrease of photosynthetic activity and stomata conductance at leaf level and the decrease of biomass at individual level were observed when the OH radical generating solution (photo-Fenton reagent) that was fumigated on needles of red pine seedlings for 2-3 months. Interestingly, the influence of OH much diminished when mannitol (radical scavenger) was added into the fumigating solution in the exposure experiment and thus mannitol effectively controlled the toxic effect of OH to pine trees. Moreover, a growth model for pine trees showed that the decrease of photosynthetic production of pine needles with OH radical exposure would reduce biomass quantity and finally cause the death of tree after year-to-year exposure of OH producing substances. A numerical simulation examined emission trends of nitrogen oxides and sulfur dioxide from various anthropogenic sources in Hiroshima prefecture. In the prefecture, stationary sources such as iron and steel industry are major emitters of these pollutants. However, with the development of new technologies for saving the energy and cost, the emission of these pollutants will be lower by 20-30% from 1990 to 2010. This decrease of major air pollutant emissions would result in significant improvement of air pollution in the prefecture and thus further pine forest decline would be unlikely. Less