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

这一博士后研究奖学金的重点是调查大气中的氨基酸及其对大气颗粒物中氮含量的贡献。它将建立一种仪器方法来表征气相和颗粒相中的氨基酸。将对最近几次实地活动的样本进行氨基酸含量分析。该项目将提高对导致氨基酸排放的自然和人为生物活动如何影响地球氮循环的理解。拟议项目的具体目标是：(1)利用化学标准校准半挥发性热解吸气溶胶气相色谱/质谱仪(SV-TAG)，并将其与气相仪器、簇式化学电离质谱仪(CLISCIMS)和粒子相仪器(GCxGC-EI/VUV-HR-TOFMS)进行比较；(2)从美国东南部亚马逊雨林和室内教室以前的实地活动中收集的SV-Tag数据和过滤样本中识别和量化氨基酸；以及(3)确定不同环境中大气气溶胶中目标游离氨基酸的分配系数。预测的分配系数和测量的分配系数之间的巨大差异表明，游离氨基酸在颗粒中凝聚和反应。这支持了这样一种假设，即氨基酸在颗粒相中反应形成稳定的低挥发性化合物，这些化合物有助于在大气颗粒和雾/云滴中观察到过量的氮(即总氮和无机氮之间的差异)。

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.