Biogenic Sources of Oxygenated Hydrocarbons in the Troposphere

植被排放的挥发性有机化合物（VOCs）对大气化学的影响正受到越来越多的关注，特别是因为它们在光化学烟雾形成中起着核心作用。过去的研究主要集中在挥发性有机化合物的碳氢化合物成分上，但最近在农村森林的空气中发现了大量的含氧碳氢化合物（OHC），如甲醇和丙酮，这导致了关于它们的起源和在对流层化学中的作用的问题。初步测量表明，与异戊二烯的排放相似，叶片可以以很高的速率排放甲醇，针叶树的芽也可以释放大量的丙酮，这表明植被是挥发性热碳的重要来源。该提案解决了几个关键问题。1)各种植物排放多少甲醇和丙酮？2)哪些不同的植物部位（如芽、叶、皮等）会释放甲醇和丙酮？3)环境、物候、季节和植物胁迫如何影响甲醇和丙酮的排放？环境和应力的影响将在受控的实验室实验中进行检验。来自不同植物科的热碳通量将作为南方环境中的农村氧化剂（ROSE II）研究的一部分（1992年夏季）进行评估，并从博尔德地区的实地调查中进行评估。通量将测量使用芽，叶，枝和茎外壳与热含量分析气相色谱法。这项工作将提供工厂甲醇和丙酮排放的第一个全面概述，这将有助于对流层化学的大气建模，特别是农村地区，并将在含甲醇燃料上线之前提供大气甲醇的自然来源估计。

The impacts of volatile organic compounds (VOCs emitted by vegetation on atmospheric chemistry are under increasing scrutiny, especially since they play a central role in photochemical smog formation. Past investigations have focused on hydrocarbon components of VOC's, but recently large quantities of oxygenated hydrocarbons (OHC's), such as methanol and acetone, have been found in the air of rural forests, leading to questions about their origins and roles in tropospheric chemistry. Preliminary measurements indicate that methanol can be emitted by leaves at high rates, similar to that for isoprene emission, and that conifer buds emit substantial quantities of acetone, suggesting that vegetation is a significant source of volatile OHC's. The proposal addresses several key questions. 1) How much methanol and acetone are emitted by various species of plants? 2) What different plant parts (e.g., buds, leaves, bark, etc.) emit methanol and acetone? 3) How do environment, phenology, season, and plant stress influence methanol and acetone emissions? The effects of environment and stresses will be examined in controlled laboratory experiments. Fluxes of OHC's from different plant families will be assessed as part of the Rural Oxidants in a Southern Environment (ROSE II) study in a southeastern forest (summer 1992), and from field surveys in the boulder area. Fluxes will be measured using bud, leaf, branch, and stem enclosures with OHC analysis by gas chromatography. This work will provide the first comprehensive overview of plant methanol and acetone emissions, which will be useful in atmospheric modeling of tropospheric chemistry, particularly of rural areas, and will provide estimation of natural sources of atmospheric methanol before methanol-containing fuels come on line.