An Experimental Data Base and Modeling Effort to Describe the Atmospheric Gas-Aerosol Mass Transfer of Semi-Volatile Organics

描述半挥发性有机物大气气体-气溶胶传质的实验数据库和建模工作

• 批准号: 9408548
• 负责人: Richard Kamens
• 金额: $ 36.5万
• 依托单位: University of North Carolina at Chapel Hill
• 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: 1994-09-15 至 1998-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9408548&HistoricalAwards=false
• 关键词: Experimental; Data; Base; Modeling; Effort

The purpose of this research is to improve our understanding of the factors that control the gas to aerosol phase distribution of semi-volatile organic compounds. Results from this program will provide modelers with tools to predict vaporization and condensation of semi-volatiles as gas and particle concentrations change with time. Most of the current efforts to predict organic partitioning have been based on equilibrium theory. Although these efforts have substantially advanced our understanding of the partitioning process under ideal conditions, there are strong indications that atmospheric equilibrium between the gas and particle phases may not be established for most compounds of interest over relatively short time scales (minutes to hours). To obtain experimental data to develop and test models of semi-volatile mass transfer between the gas and particle phases, combustion emissions will be aged in a large 190cm3 outdoor Teflon film environmental chamber. Polynuclear aromatic hydrocarbons (PAHs) will be used as example compounds, but the methodology will be applicable to other organic semi-volatile toxics. Net PAH loss rates from particles and the gas phase will be monitored. Rates of PAH mass transfer to the from the particles will be estimated using a new inner particle diffusion model which considers mass transfer in a liquid organic layer surrounding the particle. Three different types of particles will be used. They will be generated from wood, diesel and coal combustion to represent particle types which have different amounts of a "liquid phase" surrounding an inner carbon core. It is expected that the amount and type of organic material that forms this outer layer of the particle will strongly influence inner organic particle diffusion, enthalpies of desorption from the surface, and ultimately rates of particle semi- volatile uptake and loss. By changing the concentration of semi-volatile vapors and/or particles in the chamber, an d thereby perturbing the equilibrium between gas and particle phase organic, these researchers will be able to investigate rates of semi-volatile sorption (condensation) and evolution to and from particles. To radically alter equilibrium conditions, some experiments will be conducted by passing combustion emissions through a large gas stripper/denuder to remove the gas phase semi-volatile component before particles enter the chamber. Semi-volatile deuterated PAH will be added to the gas phase to observe rates of mass transfer to the particles.

本研究的目的是提高我们的理解的因素，控制的气体气溶胶相分布的半挥发性有机化合物。 该计划的结果将为建模人员提供工具，以预测气体和颗粒浓度随时间变化时半挥发物的蒸发和冷凝。 目前大多数预测有机分配的努力都是基于平衡理论。 虽然这些努力大大提高了我们对理想条件下的分配过程的理解，但有强烈的迹象表明，大多数感兴趣的化合物在相对较短的时间尺度（分钟至小时）内可能无法建立气相和颗粒相之间的大气平衡。 为了获得实验数据，以开发和测试气相和颗粒相之间的半挥发性传质模型，将在一个大型190立方厘米的室外聚四氟乙烯薄膜环境室中对燃烧排放物进行老化。 多环芳烃（PAH）将被用作示例化合物，但该方法将适用于其他有机半挥发性毒物。 将监测颗粒和气相中PAH的净损失率。 PAH从颗粒的传质速率将估计使用一个新的内部颗粒扩散模型，该模型认为在颗粒周围的液体有机层的传质。 将使用三种不同类型的颗粒。 它们将由木材、柴油和煤燃烧产生，代表内部碳核周围有不同数量的“液相”的颗粒类型。 预期形成颗粒的该外层的有机材料的量和类型将强烈影响内部有机颗粒扩散、从表面解吸的速率以及最终颗粒半挥发物吸收和损失的速率。 通过改变室内半挥发性蒸气和/或颗粒的浓度，从而扰乱气相和颗粒相有机物之间的平衡，这些研究人员将能够研究半挥发性吸附（冷凝）和从颗粒演变的速率。 为了从根本上改变平衡条件，将进行一些实验，使燃烧排放物通过一个大型气体汽提塔/扩散器，在颗粒进入燃烧室之前除去气相半挥发性组分。 将半挥发性氘代PAH添加到气相中，以观察向颗粒的传质速率。