Time-Resolved Electrospray Mass Spectrometric Studies of Atmospheric Gas-liquid Reactions

大气气液反应的时间分辨电喷雾质谱研究

• 批准号: 1238977
• 负责人: Michael Hoffmann
• 金额: $ 67.43万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1238977&HistoricalAwards=false
• 关键词: Time; Resolved; Electrospray; Mass; Spectrometric

Important but poorly constrained multiphase chemical pathways limit current understanding of the atmospheric processing and global budgets of volatile organic compounds. Electrospray mass spectrometry (ES-MS) is a powerful tool with which to investigate interfacial reactions on liquid microjets at high temporal resolution. The approach allows simultaneous detection of reactants, primary products, and intermediates in the absence of secondary chemistry for a wide variety of chemical reactions under realistic conditions. Through this project, the PI will incorporate a technique of gas-beam modulation and pulsed ion-gating detection to his existing coupled reactor and ES-MS system. The new approach will resolve reactive events on surfaces of water droplets in the absence of an applied external field. The new instrument will be used to investigate the heterogeneous chemistry of biogenic gases on the surface of mildly acidic water. Previous evidence indicates that the weakly hydrated H3O+ in small water clusters is able to protonate non-alkane organic gases at the air-water interface below pH 4. It is likely that biogenic olefins would be similarly protonated and engage in cationic oligomerization on typical environmental surfaces. This phenomenon would provide a universal mechanism for the dry deposition of most volatile organic gases. The project will addresses important issues in global atmospheric chemistry using innovative experimental approaches based on a newly proposed technique. Results are expected to fill outstanding gaps in current understanding of the atmospheric chemistry of biogenic gases and secondary aerosol formation and provide fundamental insight into the scavenging and subsequent air-to-water transfer of atmospheric CO2 on water. The project will (1) help resolve multi-phasic interfacial processes that are important to atmospheric chemistry and thereby lay the foundation of more realistic model mechanisms and (2) expose students to new, wider perspectives and skills in global environmental chemistry. Education and outreach activities include mentoring a postdoctoral fellow, a graduate student, and undergraduate students. Educational opportunities will be extended to community college students (through a partnership with Oak Crest Institute of Science) and to members of traditionally underrepresented groups (through Caltech's MURF program and a collaboration with Pasadena City College).

重要的，但约束不良的多相化学途径限制了目前的大气处理和挥发性有机化合物的全球预算的理解。电喷雾质谱（ES-MS）是一种高时间分辨率研究液体微射流界面反应的有力工具。 该方法允许同时检测的反应物，初级产品，和中间体的情况下，在现实条件下的各种各样的化学反应的二次化学。通过这个项目，PI将把气体束调制和脉冲离子门检测技术结合到他现有的耦合反应器和ES-MS系统中。新方法将解决水滴表面的反应事件，在没有外加场的情况下。新仪器将用于研究微酸性水表面生物成因气体的非均相化学。以前的证据表明，弱水合H3 O+在小的水簇是能够质子化非烷烃有机气体在空气-水界面低于pH 4。很可能，生物成因的烯烃将类似地质子化，并在典型的环境表面上进行阳离子低聚。这种现象将为大多数挥发性有机气体的干沉积提供一种普遍的机制。该项目将利用基于一种新提出的技术的创新实验方法，解决全球大气化学方面的重要问题。结果预计将填补突出的空白，目前的理解大气化学的生物成因的气体和二次气溶胶的形成，并提供基本的洞察大气CO2的清除和随后的空气到水的转移对水。该项目将（1）帮助解决对大气化学很重要的多相界面过程，从而为更现实的模型机制奠定基础，（2）让学生接触到全球环境化学中新的，更广泛的视角和技能。教育和推广活动包括指导博士后研究员，研究生和本科生。教育机会将扩大到社区大学的学生（通过与橡树冠科学研究所的合作）和传统上代表性不足的群体（通过加州理工学院的MURF计划和与帕萨迪纳城市学院的合作）的成员。