Organic Aerosol Dynamics: Single Particles and Modest Driving Forces

在这项由美国国家科学基金会化学部环境化学科学项目资助的项目中，卡内基梅隆大学大气粒子研究中心的Neil Donahue教授和Ryan Sullivan教授将研究在大气中常见条件下有机气溶胶的混合。大气颗粒物由丰富的混合物组成，通常在单个颗粒中含有数千种不同的有机化合物。有机化合物形成混合物的方式可以深刻地影响颗粒从微小尺寸(由几个分子组成的簇)到影响人类健康和气候的尺寸(直径约100纳米)以及它们的最终尺寸的速度。作为美国国家科学院科学和工程大使计划的一部分，该研究团队还将这项研究的结果与气候和健康影响的更广泛问题结合起来。该团队将探索单个颗粒的行为，无论是在隔离状态下还是在气溶胶悬浮液中，以测量精心准备的简单混合物和由更易挥发的前体在大气中氧化形成的二次化合物组成的丰富混合物的这些关键性质。一种关键的方法将是在不同的容器中制备两种不同的气雾剂悬浮液，通常使用同位素标记(D或13C)，以确保组成的质谱图彼此完全不同。在将两种悬浮液组合后，研究人员将监测单个粒子质量谱的演变，同时两个群体的组成通过气相交换进行交换(如果交换的话)。在某些情况下，如燃烧室温度和湿度等变量会有所不同。交换率和最终稳定混合态都将是关键的观察量。

In this project funded by the Environmental Chemical Sciences program in the Division of Chemistry of NSF, Professors Neil Donahue and Ryan Sullivan of the Carnegie Mellon University Center for Atmospheric Particle Studies will investigate the mixing of organic aerosols under conditions typically found in the atmosphere. Atmospheric particles consist of rich mixtures, often containing thousands of different organic compounds in a single particle. The way organic compounds form mixtures can profoundly influence how rapidly particles grow from tiny sizes (clusters of a few molecules) up to sizes that influence human health and climate (of order 100 nm in diameter) as well as their ultimate size. The research team also engages in outreach, combining the results of this research with broader issues of climate and health effects as part of the Science and Engineering Ambassadors program of the National Academy of Sciences. The team will probe the behavior of individual particles, either in isolation or in aerosol suspensions, to measure these key properties for both carefully prepared simple mixtures and rich mixtures consisting of secondary compounds formed via atmospheric oxidation of more volatile precursors. A key method will be to prepare two different aerosol suspensions in separate containers, often using isotopic labels (D or 13C) to ensure that the constituent mass spectra are completely distinct from one another. After combining the two suspensions, the researchers will then monitor the evolution of individual particle mass spectra while the constituents of the two populations interchange (if they do) via gas-phase exchange. In some cases variables such as chamber temperature and humidity will be varied. Both the rates of exchange and the ultimate stable mixing state will be key observables.