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

这个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氮含量的贡献。 它将建立一种表征气相和颗粒相氨基酸的仪器方法。 将对最近几次田间活动的样品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认识。 拟议项目的具体目标是：（1）通过使用化学标准品校准针对目标氨基酸的半挥发性热解吸气溶胶气相色谱/质谱仪（SV-TAG），并将其与气相仪器集束化学电离质谱仪（Cluster Chemical Ionization Mass Spectrometer）进行比较。（Cluster CIMS）和粒子相仪器，电子碰撞或真空紫外电离二维气相色谱与高分辨率飞行时间质谱联用（2）从SV-TAG数据和过滤样品中鉴定和定量氨基酸，所述SV-TAG数据和过滤样品在美国东南部亚马逊雨林和室内教室中的先前实地活动期间收集;（3）测定目标游离氨基酸在不同环境气溶胶中的分配系数。预测的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。这支持了氨基酸在颗粒相中反应形成稳定的低挥发性化合物的假设，所述化合物有助于观察到的过量氮（即，总氮量和无机氮量之间的差异）。

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.