Free Radical Kinetics Important in Atmospheric Aerosols

自由基动力学在大气气溶胶中很重要

• 批准号: 9812680
• 负责人: John Barker
• 金额: $ 45万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-10-01 至 2003-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9812680&HistoricalAwards=false
• 关键词: Free; Radical; Kinetics; Important; Atmospheric

Rate constants for free radical reactions in the liquid phase will be measured in the laboratory to determine the ionic strength, pH, and temperature dependence of several important reaction systems over a range of variables relevant to the atmosphere. Earlier measurements do not extend to the very high electrolyte concentrations that can occur in atmospheric aerosols. The focus of this work will be on the reactions of the nitrate radical with halogen species which are important to understand "halogen activation". This is a poorly understood process by which halides dissolved in aerosols are oxidized to yield photochemically active gas phase halogen-containing species. These can be photolyzed by sunlight and produce free halogen atoms, which attack gas phase ozone and other trace atmospheric constituents. These processes have been implicated in observed tropospheric ozone depletion events shortly after polar sunrise in the Arctic. Free radical reactions in the aqueous phase are initiated by photodissociation of precursors and by the solvation of gas phase free radicals. The measurements will be performed by using the laser flash photolysis/time-resolved absorption method. The experimental conditions are controlled in order to isolate the effects of ionic strength, pH, temperature, and any other variables desired. The rate constants which result from this work can be used directly in atmospheric models.

将在实验室中测量液相自由基反应的速率常数，以确定几个重要反应系统在一系列与大气相关的变量上的离子强度、pH 和温度依赖性。早期的测量并未扩展到大气气溶胶中可能出现的非常高的电解质浓度。这项工作的重点是硝酸根与卤素的反应，这对于理解“卤素活化”很重要。这是一个人们知之甚少的过程，通过该过程，溶解在气溶胶中的卤化物被氧化，产生光化学活性的气相含卤素物质。它们可以被阳光光解并产生游离卤素原子，从而攻击气相臭氧和其他微量大气成分。这些过程与北极极地日出后不久观测到的对流层臭氧消耗事件有关。水相中的自由基反应是通过前体的光解和气相自由基的溶剂化引发的。测量将使用激光闪光光解/时间分辨吸收方法进行。控制实验条件以隔离离子强度、pH、温度和任何其他所需变量的影响。这项工作得出的速率常数可以直接用于大气模型。