Laboratory Studies of Heterogeneous Gas-Liquid Interaction of Atmospheric Trace Gases

大气痕量气体非均相气液相互作用的实验室研究

• 批准号: 9310407
• 负责人: Paul Davidovits
• 金额: $ 45.71万
• 依托单位: Boston College
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-09-01 至 1997-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9310407&HistoricalAwards=false
• 关键词: Laboratory; Studies; Heterogeneous; Gas; Liquid

93100470 Davidovits Heterogeneous reaction pathways involving aqueous droplets in clouds and fogs are important conduits for chemical transformation of atmospheric trace gases both in the troposphere and in the stratosphere. During the past eight years in a collaborative effort between the Chemistry Department at Boston College and the Center for Chemical and Environmental Physics at Aerodyne Research, Inc., supported in part by the National Science Foundation, two novel and powerful techniques have been developed for studying gas uptake processes and for measuring mass accommodation coefficients of trace atmospheric species on water and other liquids. These techniques can also yield information about the nature of chemical interactions at the gas-liquid interface. In the first method, suitable for measuring relatively large gas uptakes, the gas phase species interacts with a controllable stream of small (50 to 250 um radius) monodispered droplets of known size, temperature and chemical composition. A version of this apparatus using sulfuric acid droplets has also been built to study stratospherically important processes down to a temperature of -50oC. In the second method, used to study gases with relatively smaller uptakes, the trace gas is contained in controlled bubbles rising through the liquid of interest. During the past two NSF support periods the uptake of more than thirty gas phase species has been studied as a function of temperature over a wide range of atmospherically relevant conditions. The species studied include SO2 and reduced sulfur compounds, H2O2, N2O5, HNO3, HCl, ClNO3 and N2O5 the uptake by aqueous sulfuric acid droplets was also measured as a function of temperature down to -50oC. This work provided values for the parameters determining uptake for both tropospherically and stratospherically important species and it led to the formation of a quantitative model for the uptake of nonreactive gases. Further, important features of chemical interactions at the gas-liquid interface were noted. In some cases, such as formaldehyde and phosgene, the uptake was entirely consistent with the bulk aqueous chemistry of the species. But in other cases, such as the uptake of sulfur dioxide and acetaldehyde, results were not explainable by bulk phase chemistry. Instead, these results indicate that reactions at the gas-liquid interface dominate the gas or the liquid phase. Reactions may be orders of magnitude faster at the interface than either in the gas or in the liquid phases. It was also observed, that in the process of uptake, some species such as SO2, form a chemisorbed complex at the gas-liquid interface which is likely to participate in the heterogeneous chemistry of the species. The work plan in this grant will continue to pursue the study of atmospherically important heterogeneous processes. The research will include gas uptake and co-deposition studies for NO, NO2, NO3, N2O5, HNO3, HONO, NH3, SO2, CH2O and OH. Experiments will be constructed as a function of temperature with aqueous solutions, with sulfuric acid and with nitrosyl sulfuric acid solutions. The effect on heterogeneous processes of photochemistry, surface charge and various atmospherically relevant additives will be examined. The two major objectives of the research studies are: a) To continue the measurement of parameters required to assess the heterogeneous chemistry of species important to troposphere an stratosphere. b) To obtain a general, predictive understanding of chemistry at the gas-liquid interface.

93100470 Davidovits 涉及云和雾中水滴的异质反应途径是对流层和平流层中大气痕量气体化学转化的重要途径。 在过去的八年中，波士顿学院化学系与 Aerodyne Research, Inc. 化学与环境物理中心在美国国家科学基金会的部分支持下共同努力，开发了两种新颖而强大的技术，用于研究气体吸收过程以及测量微量大气物质对水和其他液体的质量调节系数。 这些技术还可以产生有关气液界面化学相互作用性质的信息。 在第一种方法中，适合测量相对较大的气体吸收量，气相物质与已知尺寸、温度和化学成分的小（50至250微米半径）单分散液滴的可控流相互作用。 该设备使用硫酸液滴的一个版本也已建成，用于研究温度低至 -50oC 的平流层重要过程。 在第二种方法中，用于研究吸收相对较小的气体，痕量气体包含在通过感兴趣的液体上升的受控气泡中。 在过去的两个 NSF 支持期间，对三十多种气相物质的吸收作为在各种大气相关条件下的温度函数进行了研究。 研究的物质包括 SO2 和还原的硫化合物、H2O2、N2O5、HNO3、HCl、ClNO3 和 N2O5，还测量了含水硫酸液滴的吸收量，作为低至 -50oC 的温度的函数。 这项工作提供了确定对流层和平流层重要物种吸收的参数值，并导致形成非反应性气体吸收的定量模型。 此外，还注意到气液界面化学相互作用的重要特征。 在某些情况下，例如甲醛和光气，吸收量与该物种的大部分水化学性质完全一致。 但在其他情况下，例如二氧化硫和乙醛的吸收，结果无法用体相化学来解释。 相反，这些结果表明气-液界面的反应主导气相或液相。 界面处的反应可能比气相或液相中的反应快几个数量级。 还观察到，在吸收过程中，某些物质（例如 SO2）在气液界面形成化学吸附复合物，这可能参与该物质的非均相化学。 这笔赠款的工作计划将继续进行对大气重要的非均质过程的研究。 该研究将包括 NO、NO2、NO3、N2O5、HNO3、HONO、NH3、SO2、CH2O 和 OH 的气体吸收和共沉积研究。 将使用水溶液、硫酸和亚硝酰硫酸溶液构建作为温度函数的实验。 将研究对光化学、表面电荷和各种大气相关添加剂的异质过程的影响。 研究的两个主要目标是： a) 继续测量评估对流层和平流层重要物种的异质化学所需的参数。 b) 获得对气液界面化学的一般性、预测性理解。