Chemical and Spectroscopic Studies of Stratospheric Aerosols

I型极地平流层云（PSCs）上的化学反应目前被认为是破坏极地臭氧的关键步骤。虽然I型psc被认为是由硝酸/水蒸气（HNO3/H2O）混合物组成，但它们的确切化学成分和相仍然不确定。该研究项目将使用红外、可见光和紫外光谱来确定I型psc的化学成分。首先，将在较宽的波长范围内测量NHO3/H2O混合物的光学常数，以便与I型psc的现场观测结果进行比较。还将进行模型I型PSC薄膜生长的实验室研究。这些研究将使用原位FTIR光谱作为PSC成核和生长过程中凝聚材料的化学成分和相的探针。除了利用光谱学来鉴定PSCs外，新的光谱学实验将研究I型PSCs的表面反应。硝酸氯（CIONO2）与盐酸（HCl）在I型PSCs上的反应目前被认为是促进臭氧损失的单一最重要的非均相反应。以前的工作表明，这种反应强烈地依赖于相对湿度的增加。大角度反射FTIR光谱将用于探测CLONO2与HCI在I型PSC膜上的表面反应。在此过程中，缩合相的表面光谱探针将有助于深入了解这一重要的多相反应的复杂机理。除了PSCs上的化学反应外，现在对全球平流层硫酸盐气溶胶（SSA）层的非均相化学也有了更高的兴趣。在过去十年中观测到的臭氧下降趋势可能与背景和火山ssa上的化学反应有关。该项目将研究ssa的化学和物理性质，ssa主要由硫酸和水蒸气（H2SO4）和（H2O）组成。还将进行光谱实验，以表征低温液体和冷冻硫酸膜，以便与SSAs的现场观测结果进行比较。此外，还将对SSAs的化学反应性进行研究。对反应物和生成物的气相和凝聚相检测的结合将用于获得凝聚相反应的更完整的图像。最初的研究将集中在HOx储层物种在硫酸中的吸收和反应性，作为酸的组成和相的函数。

9321582 Tolbert Chemical reactions on type I polar stratospheric clouds (PSCs) are currently believed to be a key step in polar ozone destruction. Although type I PSCs are thought to be composed of nitric acid/water vapor (HNO3/H2O) mixtures, their exact chemical composition and phase are still uncertain. This research project will use infrared, visible, and ultraviolet spectroscopy to determine the chemical composition of type I PSCs. First, the optical constants for NHO3/H2O mixtures will be measured over a wide wavelength range for use in comparisons with field observations of type I PSCs. Laboratory studies of model type I PSC film growth will also be performed. These studies will use in situ FTIR spectroscopy as a probe of the chemical composition and phase of the condensed material during PSC nucleation and growth. In addition to using spectroscopy to identify PSCs, new spectroscopic experiments will study surface reactions on type I PSCs. The reaction of chlorine nitrate (CIONO2) with hydrochloric acid (HCl) on type I PSCs is currently believed to be the single most important heterogenous reaction promoting ozone loss. Previous work has shown that this reaction depends strongly on the relative humidity is increased. Large angle reflectance FTIR spectroscopy will be used to probe the surface reaction of CLONO2 with HCI on model type I PSC films. Surface spectroscopic probes of the condensed phase during should yield insight into the complex mechanism of this important heterogenous reaction. In addition to chemical reactions on PSCs, there is now heightened interest in heterogenous chemistry on the global stratospheric sulfate aerosol (SSA) layer. Chemical reactions on background and volcanic SSAs may be responsible for the down ward trend in ozone observed in the last decade. This project will investigate the chemical and physical properties of SSAs, composed primarily of sulfuric acid and water vapors (H2SO4) and(H2O). Spectroscopi c experiments will also be performed to characterize low temperature liquid and frozen sulfuric acid films representative of SSAs fro use in comparisons with field observations of SSAs. In addition, the chemical reactivity of SSAs will be studied. A combination of gas phase and condensed phase detection of reactants and products will be used to obtain a more complete picture of the condensed phase reactions. Initial studies will focus on the uptake and reactivity of HOx reservoir species in sulfuric acid as a function of composition and phase of the acid.