Investigating Fundamental Chemical and Physical Processes Affecting Gas-Particle Partitioning Using Levitated Droplet-Mass Spectrometry

该奖项由化学学部环境化学科学项目资助。哈佛大学的Frank Keutsch教授和他的学生研究了分离空气和大气中颗粒（气溶胶）表面之间化合物的基本过程。空气和存在于空气中的固体表面之间的这种分配尚不清楚，然而，由于不完全混合、物理屏障和/或气溶胶颗粒上的化学反应，一种相可能优于另一种相。对单个气溶胶颗粒进行实验室研究，以分离和调查化合物如何以及为何粘附在其表面。这些实验研究为改进关于气溶胶形成和这些粒子随时间（老化）变化的计算机模型提供了基本参数。这项研究很重要，因为它可能最终改进与空气质量以及人类和动物健康相关的区域和全球气溶胶模型。Keutsch教授还设计了实验室实验，将系统方法引入本科教育。这种方法不仅考虑单个反应，而且考虑存在于整个系统不同部分（在这种情况下，气相和固相）之间的耦合化学和物理反馈。他的学生学习仪器设计和反应在平衡和远离平衡。此外，在剑桥，麻萨诸塞州高中，代表性不足的高中生得到指导，并在研究实验室工作，学习与该领域的其他人交流他们的研究，并获得对自己参与科学领域能力的信心。采用了一种新的方法，将单个微米级粒子的悬浮与质谱（MS）检测相结合，用于研究气溶胶分配。这项技术允许在大气相关的时间尺度上测量液滴的分子水平演变。分子水平检测是一种新颖的方法，可能会推动捕获液滴方法的发展。在进一步优化捕集液滴质谱后，研究了非理想混合、低聚物形成、过渡金属络合物光化学和气溶胶物理性质在气-颗粒分配中的作用等具体研究问题。这项研究是与化学家和大气科学合作完成的。将结果与最先进的模型进行比较，这些模型改进了模型中基本化学和物理过程的表示，从而提高了预测能力。该奖项反映了美国国家科学基金会的法定使命，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。

This award is supported by the Environmental Chemical Sciences Program of the Division of Chemistry. Professor Frank Keutsch of Harvard University and his students investigate the fundamental processes involved in separating compounds between the air and the surface of particles (aerosols) in the atmosphere. This portioning between the air and the surfaces of solids that are present in the air is poorly understood however, one phase may be preferred over the other due to incomplete mixing, physical barriers, and/or chemical reactions on the aerosol particles. Laboratory studies are conducted on single aerosol particles to isolate and investigate how and why compounds stick to their surfaces. These experimental studies provide fundamental parameters for improving computer models on aerosol formation and changes in these particles with time (ageing). This research is important as it may ultimately improve regional and global models of aerosols, which are relevant to air quality and human and animal health. Professor Keutsch also designs laboratory experiments to introduce a systems approach to undergraduate education. This approach considers not only individual reactions but the coupled chemical and physical feedbacks that exist between different parts of the whole system (in this case, the gas and solid phases). His students learn about instrumentation design and reactions at and far from equilibrium. In addition, underrepresented high school students at Cambridge, MA high schools are mentored and work in the research laboratory learning to communicate their research to others in the field and gaining confidence in their abilities to participate in scientific fields. A new approach is used to study aerosol partitioning that combines levitation of individual micron-sized particles with mass-spectrometric (MS) detection. This technique allows the measurement of the molecular-level evolution of a droplet over atmospherically relevant time scales. Molecular-level detection is a novel approach that may advances trapped droplet methods. After further optimization of the trapped-droplet MS, specific research questions related to the role of non-ideal mixing, oligomer formation, transition metal complex photochemistry, and aerosol physical properties in gas-particle partitioning are addressed. This research is done in collaboration with chemists and atmospheric sciences. Results are compared with state-of-the-art models which improve the representation of the fundamental chemical and physical processes in the models, and hence, improve predictive capabilities.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.