AGS-PRF: Molecular Level Characterization of Amino Acids in Atmospheric Aerosols

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This Postdoctoral Research Fellowship is focused on the investigation of amino acids in the atmosphere and their contribution to the nitrogen content of atmospheric particles. It will establish an instrumental method for characterizing amino acids in gas and particle phases. Samples from several recent field campaigns will be analyzed for amino acid content. This project will improve the understanding of how biological activities, both natural and anthropogenic, that lead to the emission of amino acids influence Earth's nitrogen cycle. The specific objectives of the proposed project are to: (1) Calibrate the Semi-Volatile Thermal desorption Aerosol Gas chromatograph/mass spectrometer (SV-TAG) for targeted amino acids by using chemical standards, and compare it to a gas phase instrument, Cluster Chemical Ionization Mass Spectrometer (Cluster CIMS), and a particle phase instrument, two-dimensional GC with electron impact or vacuum UV ionization coupled to a high resolution time-of-flight MS (GCxGC-EI/VUV-HR-TOFMS); (2) Identify and quantify amino acids from SV-TAG data and filter samples collected during previous field campaigns in the Amazon Rainforest, Southeastern United States, and an indoor classroom; and (3) Determine the partitioning coefficients of targeted free amino acids in atmospheric aerosols from various environments. Large discrepancies between predicted and measured partitioning coefficients indicate that free amino acids are condensing and reacting in the particles. This supports the hypothesis that amino acids react in the particle phase to form stable, low volatility compounds that contribute to the observed excess nitrogen (i.e., difference between total nitrogen and inorganic nitrogen amounts) in atmospheric particles and fog/cloud droplets.