Accelerated Chemistry In Aerosol Droplets Relevant To The Atmosphere

化学系的环境化学科学项目支持特拉华州大学的Murray约翰斯顿教授研究气溶胶液滴中可能有助于大气中有机颗粒物形成的化学反应。空气污染对健康的主要影响来自臭氧和颗粒物。本项目研究空气中的水如何帮助挥发性有机化合物形成有机颗粒物，其方式无法通过研究散装水溶液中的化学反应来预测。 该项目还通过在鼓励多学科创新和公共宣传的环境中对研究生进行培训，促进科学工作者的发展。 气溶胶流动反应器用于研究硫酸铵水溶液液滴表面上的化学反应，该反应将联合收割机两种挥发性单体反应物结合以得到非挥发性二聚体产物。 这些反应包括生成羟醛的脱氢-醛反应、生成半缩醛的脱氢-醇反应和生成酯的醇-酸反应。 反应器系统能够精确控制初始液滴尺寸和组成，包括水含量、离子强度和酸度。 这些变量的系统控制提供了深入了解反应机制。 反应的中间体和产物进行了表征，并在可能的情况下，用各种在线质谱方法进行定量。这些方法包括使用纳米气溶胶质谱仪进行元素分析，其基于氮硫摩尔比测量液滴酸度，以及使用液滴辅助电离和萃取电喷雾电离进行分子分析。 该项目支持的学生在环境化学、分析化学和纳米科学方面得到广泛的培训。 该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Environmental Chemical Sciences Program of the Division of Chemistry supports Professor Murray Johnston of the University of Delaware to investigate chemical reactions in aerosol droplets that may contribute to formation of organic particulate matter in the atmosphere. The main health impacts of air pollution arise from ozone and particulate matter. This project studies how water in airborne particles can assist formation of organic particulate matter from volatile organic compounds in ways that are not readily predicted by studying chemical reactions in bulk aqueous solution. This project also contributes to the development of the scientific workforce through graduate student training in an environment that encourages multidisciplinary innovation and public outreach. An aerosol flow reactor is used to study chemical reactions on the surface of aqueous ammonium sulfate droplets that combine two volatile monomer reactants to give a nonvolatile dimer product. These reactions include aldehyde-aldehyde reactions to produce an aldol, aldehyde-alcohol reaction to produce a hemiacetal, and alcohol-acid reaction to produce an ester. The reactor system has the ability to precisely control initial droplet size and composition including water content, ionic strength and acidity. Systematic control of these variables provides insight into reaction mechanisms. Intermediates and products of the reactions are characterized and, where possible, quantified with a variety of online mass spectrometry methods. These methods include elemental analysis with the nano aerosol mass spectrometer, which gives a measure of droplet acidity based on the nitrogen-to-sulfur mole ratio, and molecular analysis with droplet assisted ionization and extractive electrospray ionization. Students supported by the project are broadly trained in environmental chemistry, analytical chemistry and nanoscience. They bring environmental topics to the attention of scientists and non-scientists alike through various outreach events.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.