Nanoscale Visualization and Understanding of Atmospheric Aerosol Dissolution Kinetics in Aqueous Organic Droplets

NSF化学部的环境化学科学计划资助了由Akua Asa-Awuku和Taylor Woehl教授领导的这项研究。该项目研究大气中的有机蒸气与大气颗粒物（也称为气溶胶）之间的相互作用。特别令人感兴趣的是这些气溶胶影响云的形成的能力，这反过来又对地球的气候很重要。大气颗粒物是水溶性和不溶性化合物的复杂混合物。化学家希望确定气溶胶作为有效云凝结核（CCN）的能力，但化学和物理多样性导致气溶胶和云之间的复杂相互作用。模型通常假设不溶于水的有机气溶胶不能作为CCN。气溶胶吸收水并形成液滴的过程还不完全清楚。假设部分可溶的颗粒必须首先溶解并进入水相，然后再容易地加入更多的水。但是，这种现象并没有直接看到。 该项目直接可视化在纳米尺度上CCN激活水不溶性气溶胶期间发生的过程。从这些观察结果中，研究小组对这类重要气溶胶的CCN行为有了新的机械理解。该项目为吸引多元化的STEM劳动力提供了机会。Asa-Awuku教授和Wohl教授都指导K-12学生，并参与马里兰州大学帕克分校现有的STEM推广项目。该项目重点关注有机蒸汽对水不溶性气溶胶的CCN活性的影响以及液滴冷凝过程中发生的纳米级动态过程。该项目直接可视化了CCN激活过程中发生的纳米级动态过程。这些观测结果被用来获得新的机械理解的CCN行为的这一重要类别的气溶胶。该团队利用一种新的单颗粒技术，液体细胞透射电子显微镜，以纳米级的空间分辨率在真实的时间内可视化颗粒溶解动力学和液滴生长动力学。电子显微镜数据直接与定量测量的CCN激活使用受控气溶胶表征技术。这些数据有望揭示CCN活化水不溶性气溶胶过程中发生的一系列化学和物理过程。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 NSF Division of Chemistry funds this research led by Professors Akua Asa-Awuku and Taylor Woehl. The project studies the interactions between organic vapors in the atmosphere and atmospheric particles (also known as aerosols). Of particular interest is the ability of these aerosols to affect cloud formation, which in turn is important for the Earth's climate. Atmospheric particles are complex mixtures of water-soluble and insoluble compounds. Chemists want to determine the ability of aerosols to act as effective cloud condensation nuclei (CCN), but chemical and physical diversity results in complicated interactions between aerosols and clouds. Models often assume that water-insoluble organic aerosols cannot act as CCN. The processes by which aerosols take up water and form droplets are not fully known. It is assumed that partially soluble particles must first dissolve and enter the water phase before readily adding more water. However, this phenomenon has not been directly seen. The project directly visualizes the processes that occur during CCN activation of water-insoluble aerosols on the nanometer scale. From these observations, the team derives a new mechanistic understanding of CCN behavior of this important class of aerosols. The project provides opportunities for engaging a diverse STEM workforce. Both Professor Asa-Awuku and Professor Wohl mentor K-12 students and engage with existing STEM outreach programs at the University of Maryland College Park.This project focuses on the impact of organic vapors on the CCN activity of water-insoluble aerosols and the nanoscale dynamic processes that occur during droplet condensation. The project directly visualizes nanoscale dynamic processes that occur during CCN activation. These observations are used to derive new mechanistic understanding of the CCN behavior of this important class of aerosols. The team utilizes a novel single particle technique, liquid cell transmission electron microscopy, to visualize particle dissolution kinetics and droplet growth kinetics in real time with nanometer scale spatial resolution. The electron microscopy data are directly correlated with quantitative measurements of CCN activation using controlled aerosol characterization techniques. Together these data are expected to reveal the series of chemical and physical processes occurring during CCN activation of water insoluble aerosols. These insights will contribute to a broader theoretical framework for cloud-aerosol interactions.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.