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

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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.