Laboratory Studies of Heterogeneous Chemistry in the Upper Troposphere/Lower Stratosphere

9711969托尔伯特在这个项目中，将进行与对流层上层/平流层下层有关的条件下的粒子形成和非均相化学反应的实验室研究。极地平流层云(PSCs)的组成、形成机制和丰度仍然不确定，非均相化学在对流层上层的作用也尚未确定。为了探索粒子的形成，将进行几种类型的实验。首先，利用傅里叶变换红外反射吸收光谱(RAS)对大气物质的均相成核参数和非均相成核参数进行了基本测量。将确定扩散激活能和接触参数，为形核理论提供必要的输入。其他实验室实验将探索PSCs的形成机制，特别是Ia型PSCs，其确切组成尚不清楚。此外，还将对对流层上层可能具有重要意义的非均相化学反应进行实验室研究。那里最丰富的颗粒物类型被认为是卷云、次可见卷云和硫酸盐气溶胶。将使用Knudsen池流动反应器和FTIR RAS来探测凝聚相。将研究含氧有机物与凝结在卷云颗粒上的硝酸之间可能发生的氧化/还原反应，并将进行潮解硫酸盐和结晶硫酸盐的反应性实验。

9711969 Tolbert In this project, laboratory studies of particle formation and heterogeneous chemical reactions under conditions relevant for the upper troposphere/lower stratosphere will be performed. The composition, formation mechanism and abundance of polar stratospheric clouds (PSCs) remain uncertain, and the role of heterogeneous chemistry in the upper troposphere has not been established. To probe particle formation, several types of experiments will be performed. First FTIR reflection absorption spectroscopy (RAS) will be used to make fundamental measurements of homogeneous and heterogeneous nucleation parameters for atmospheric materials. Diffusion activation energies and contact parameters will be determined to provide the necessary input for nucleation theory. Other laboratory experiments will probe the formation mechanisms of PSCs, in particular, type Ia PSCs, whose exact composition is still unknown. In addition, laboratory studies of heterogeneous chemical reactions of potential importance in the upper troposphere will be performed. The most abundant types of particles there are thought to be cirrus, subvisible cirrus, and sulfate aerosols. A Knudsen cell flow reactor coupled with FTIR RAS to probe the condensed phase will be used. Oxidation/reduction reactions that may occur between oxygenated organics and nitric acid condensed on cirrus particles will be studied, and experiments on the reactivity of deliquesced and crystalline sulfate salts will be performed.