Formaldehyde Chemical Actinometer for the Troposphere: Measurements of Photolysis Rate Coefficient, H2 and H02 Branching Ratios, and Comparison with other Ultraviolet Ligh

对流层甲醛化学光量计：光解速率系数、H2 和 H02 支化比的测量，以及与其他紫外灯的比较

• 批准号: 9422307
• 负责人: Brian Heikes
• 金额: $ 17.5万
• 依托单位: University of Rhode Island
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-09-15 至 1998-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9422307&HistoricalAwards=false
• 关键词: Formaldehyde; Chemical; Actinometer; Troposphere; Measurements

9422307 Heikes The photolysis of formaldehyde is an important intermediate step in the atmospheric oxidation of hydrocarbons and leads to the direct formation of carbon monoxide, hydrogen, and perhydroxyl radicals. The later two are produced through two different photolysis channels. The perhydroxyl channel is significant to the net photochemical production of odd-hydrogen, ozone, hydrogen peroxide, and organic hydroperoxides. Uncertainties in the photolysis rate and in the branching between the two channels lead directly to uncertainties in the oxidizing power of the atmosphere. These rates are currently estimated using modeled actinic fluxes of light, laboratory derived formaldehyde absorption cross sections, and laboratory derived quantum yields. Atmospheric gases, aerosols, and clouds confound the actinic flux calculation. This together with measurement uncertainties in the laboratory data may lead to significant errors in the photolysis rates and radical production rates from the photolysis of formaldehyde. In this project, a chemical actinometer will be constructed to measure directly the photolysis rate of formaldehyde and the product distribution. Ambient formaldehyde concentrations will also be measured. These measurements will be used in conjunction with theoretical models to test our understanding of formaldehyde photolysis and evaluate its strength as a perhydroxyl radical source. Measured photolysis rates and branching ratios will be correlated with narrow-band and broad-band UV irradiance measurements. Correlations identified will permit the use of more simple irradiance measurements to estimate formaldehyde photolysis properties.

甲醛的光解是碳氢化合物在大气中氧化的一个重要中间步骤，导致一氧化碳、氢和过羟基自由基的直接形成。后两者是通过两个不同的光解通道产生的。过羟基通道对奇氢、臭氧、过氧化氢和有机氢过氧化物的净光化学生产具有重要意义。光解速率和两个通道间分支的不确定性直接导致大气氧化能力的不确定性。这些速率目前是使用模拟光化通量、实验室衍生的甲醛吸收截面和实验室衍生的量子产率来估计的。大气气体、气溶胶和云混淆了光化通量的计算。这与实验室数据中的测量不确定性一起可能导致甲醛光解速率和自由基生成速率的显着误差。在本项目中，将构建一个化学光照度计，直接测量甲醛的光解速率和产物分布。环境甲醛浓度也将被测量。这些测量将与理论模型结合使用，以测试我们对甲醛光解的理解，并评估其作为过羟基自由基来源的强度。测量的光解速率和分支比将与窄带和宽带紫外辐照度测量相关联。确定的相关性将允许使用更简单的辐照度测量来估计甲醛的光解特性。