Organic Acid Concentrations and Fluxes over a Southeastern Forest during the Southern Oxidant and Aerosol Study (SOAS)

我们对大气化学如何影响空气质量和气候的理解中的一个关键差距是生物圈在影响大气组成方面的作用。生物圈潜在地充当氧化挥发性有机化合物（VOCs）的源和汇，使我们对生物圈-大气相互作用的解释复杂化。有机酸是一组具有不同VOC前体和潜在主要生物排放源的生物VOC氧化产物，并且可以用作生物VOC氧化的示踪剂。然而，了解它们的生物圈-大气交换是必要的解释其源，汇，在大气中的有机化合物的光化学级联的作用。 该项目的主要目标是：（1）通过定量四种关键有机酸的气相浓度，研究有机酸作为生物源VOC氧化化学示踪剂的潜力使用气相有机酸使用高分辨率化学电离飞行时间质谱法测定（甲酸、丙烯酸、甲基丙烯酸、异辛酸），和（2）为了更好地限制幅度，通过定量分析有机酸在生态系统尺度上的通量，研究了有机酸在生物圈-大气交换中的变化和控制过程。这些测量将于2013年夏季在美国东南部森林进行，作为东南部氧化剂和气溶胶研究（SOAS）的一部分。 美国东南部是异戊二烯和其他生物源挥发性有机化合物的重要来源，如挥发性有机化合物和颗粒浓度所观察到的，因此是研究有机酸及其生态系统规模通量的绝佳场所。该项目的广泛影响包括：（1）研究生的教学和培训，（2）通过扩大PI小组与其他机构和国家实验室的科学家之间的网络，加强研究基础设施，（3）提高对生物源VOC氧化和有机酸生物圈-大气交换的理解，这对于准确模拟当地空气质量和气候至关重要，（4）通过出版物和向科学界和当地（高中生、本科生、研究生）社区介绍情况，广泛传播研究和观察结果。

One of the key gaps in our understanding of how atmospheric chemistry impacts air quality and climate is the role of the biosphere in affecting the composition of the atmosphere. The biosphere potentially acts as both a source and a sink for oxidized volatile organic compounds (VOCs), complicating our interpretation of biosphere-atmosphere interactions. Organic acids are one suite of biogenic VOC oxidation products that have varying VOC precursors and potential primary biogenic emission sources, and may serve as tracers of biogenic VOC oxidation. However, understanding their biosphere-atmosphere exchange is necessary for interpreting their sources, sinks, and role in the atmosphere's photochemical cascade of organic compounds. The primary objectives of this project are: (1) To investigate the potential of organic acids to act as tracers of biogenic VOC oxidation chemistry by quantifying gas-phase concentrations of four key organic acids (formic acid, acrylic acid, methacrylic acid, pyruvic acid) using gas-phase organic acids using high resolution chemical ionization time-of-flight mass spectrometry, and (2) To better constrain the magnitude, variation and controlling process of biosphere-atmosphere exchange of organic acids by quantifying ecosystem-scale fluxes of these organic acids. These measurements will be made over a Southeastern U.S. forest as part of the Southeastern Oxidant and Aerosol Study (SOAS) in the summer of 2013. The Southeastern United States is a significant source of isoprene and other biogenic VOCs, as observed in VOC and particle concentrations, and is thus an excellent site for studying organic acids and their ecosystem-scale fluxes. The broader impacts of this project include: (1) The teaching and training of graduate students, (2) Enhanced infrastructure for research by expanding networks between the PI's group and scientists at other institutions and national labs, (3) Improved understanding of biogenic VOC oxidation and biosphere-atmosphere exchange of organic acids, which is essential for accurate modeling of air quality and climate on local, regional and global scales, and (4) Broad dissemination of the research and observations through publications and presentations to the scientific and local (high school, undergraduate, graduate students) community.