Biogenic Sources of Atmospheric Acetone and Other Carbonyls

这项提议涉及生物圈-大气层交换丙酮，一种进入地球大气层的挥发性有机化合物(VOC)，对对流层上层和平流层下层的奇数氢自由基(Hox)和背景臭氧的形成非常重要。丙酮光化学还会导致过氧乙酰硝酸盐的形成，从而隔离和传输奇氮(NOx)当量。虽然这些与丙酮有关的过程显然会影响大气的氧化能力，但全球丙酮预算仍有很大的不确定性，估计为40-60tg/yr-1，特别是在生源丙酮排放速率和生源丙酮形成机制方面。这项拟议工作的主要目标是建立丙酮和甲乙酮在植物组织中形成的潜在机制，并表征它们从植物表面释放的控制。我们还想确定某些作物是否被忽视了，因为它们是碳基排放的主要来源。该项目将包括实验室实验和通过检查由国家大气研究中心(NCAR)的科学家组织的协作实地实验的数据集进行的实地验证。计划中的实验室、温室和田间实验应产生急需的关于植被生物碳化通量的数据集，并应有助于开发一个综合的植物VOC排放模型，以解释植物碳向挥发物的分配。这一模型意义重大，因为植物通常排放1-8%的固定二氧化碳作为VOCs，而生物圈-大气交换的一个重要方面是了解植物为什么以及如何将资源用于挥发性次生化合物的生产。如果我们要预测由于人类对生物圈的影响，地球大气将发生的变化，这些信息是至关重要的。

This proposal addresses biosphere-atmosphere exchange of acetone, a volatile organic compound (VOC) that enters the Earth's atmosphere and is important in odd hydrogen radical (HOx) and background ozone formation in the upper troposphere and lower stratosphere. Acetone photochemistry also results in the formation of peroxyacetylnitrate, with resultant sequestering and transport of odd nitrogen (NOx) equivalents. While it is clear that these acetone-related processes affect the oxidative capacity of the atmosphere, there are significant uncertainties in the global acetone budget, estimated as 40-60 Tg yr-1, especially in the rates of biogenic acetone emission and the mechanisms of biogenic acetone formation. The major goal of the proposed work is to establish the underlying mechanisms of formation of acetone and methyl ethyl ketone in plant tissues, and to characterize the controls over their release from plant surfaces. We also want to determine if certain crops have been overlooked as major sources of carbonyl emissions. The project will include both laboratory experiments and field verification via examination of data sets from collaborative field experiments organized by scientists at the National Center for Atmospheric Research (NCAR). Planned laboratory, greenhouse and field experiments should produce much-needed data sets on biogenic carbonyl fluxes from vegetation, and should contribute to the development of an integrated plant VOC emission model to explain the partitioning of plant carbon into volatiles. This modeling could be significant, because plants often emit 1-8% of fixed CO2 as VOCs, and an important aspect of biosphere-atmosphere exchange is to understand why and how plants commit resources to volatile secondary compound production. Such information is vital if we are to predict changes that will occur in the Earth's atmosphere as the result of human impacts of the biosphere.