Chemical and Spectroscopic Studies of Stratospheric Aerosols

平流层气溶胶的化学和光谱研究

• 批准号: 9321582
• 负责人: Margaret Tolbert
• 金额: $ 35.5万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-04-15 至 1998-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9321582&HistoricalAwards=false
• 关键词: Chemical; Spectroscopic; Studies; Stratospheric; Aerosols

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.

9321582 Tolbert 目前认为 I 型极地平流层云 (PSC) 上的化学反应是破坏极地臭氧的关键步骤。 尽管 I 型 PSC 被认为是由硝酸/水蒸气 (HNO3/H2O) 混合物组成，但其确切的化学成分和相仍不确定。 该研究项目将使用红外、可见和紫外光谱来确定 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 的现场观察进行比较。 还将进行 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。 除了使用光谱法来识别 PSC 之外，新的光谱实验还将研究 I 型 PSC 的表面反应。 目前认为，硝酸氯 (CIONO2) 与盐酸 (HCl) 在 I 型 PSC 上的反应是促进臭氧损失的最重要的非均相反应。 先前的工作表明，这种反应强烈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 薄膜上的表面反应。 凝聚相的表面光谱探针应该可以深入了解这一重要的多相反应的复杂机制。 除了 PSC 上的化学反应外，现在人们对全球平流层硫酸盐气溶胶 (SSA) 层的异质化学也越来越感兴趣。背景和火山SSA上的化学反应可能是过去十年观察到的臭氧下降趋势的原因。 该项目将研究主要由硫酸和水蒸气 (H2SO4) 和 (H2O) 组成的 SSA 的化学和物理性质。 还将进行光谱实验来表征代表 SSA 的低温液体和冷冻硫酸膜，以便与 SSA 的现场观察进行比较。 此外，还将研究SSAs的化学反应性。 将结合反应物和产物的气相和凝相检测来获得更完整的凝相反应情况。 初步研究将集中于硫酸中 HOx 储存物种的吸收和反应性，作为酸的组成和相的函数。