Abundance and Group Reactivity of Intermediate Volatility Organic Compounds (IVOCs) in Urban Air Measured by TD-PTR-MS

本提案的主要目标是开发一种方法来量化城市空气中的中间挥发性有机化合物（IVOCs）的丰度。这些化合物含有12至18个碳原子，在柴油发动机废气中排放，被认为是有助于形成二次有机气溶胶（SOA）的反应性有机化合物的重要来源。人们对IVOC的丰度和大气化学性质知之甚少。该方案将建立一种新的方法，利用热解吸采样耦合质子转移反应质谱（TD-PTR-MS）定量空气中的IVOCs。通过这种方法，将测量IVOC烷烃的总丰度。该方法将允许通过将IVOC物质归为官能团（即，烷烃、环烷烃）或它们的分子量（即单环芳烃、萘）。该方法将用于为期四周的现场采样活动，比较IVOC丰度挥发性有机化合物（VOC）丰度测量的PTR-MS和气相色谱质谱（GC-MS），以测试的命题，即IVOC光氧化是城市SOA的主要来源。使用光反应反应室的实验室实验将用于光化学老化柴油燃料和柴油发动机排气，以建立IVOC基团与羟基自由基的反应性。这些实验将有助于现场数据的解释，并提高目前稀疏的知识IVOC的化学传输建模所需的寿命。建立一种测量方法来量化空气中IVOCs的丰度，解决了城市空气光化学和SOA形成知识的关键空白。该研究将支持和培训两名研究生和一名本科生在有机痕量气体的分析和解释。结果和使用的仪器将被纳入本科课程和高级空气质量实验室课程。研究成果将通过会议和同行评审期刊传播。研究结果将增进我们对大气中有机化合物的性质和来源的了解。公共利益将是对城市空气中柴油发动机废气的水平和影响的更定量的了解。

The primary objective of this proposal is to develop a method to quantify the abundance of intermediate volatility organic compounds (IVOCs) in urban air. These compounds contain 12 to 18 carbon atoms, are emitted in diesel engine exhaust, and are thought to be a significant source of reactive organic compounds that contribute to the formation of secondary organic aerosol (SOA). The abundance and atmospheric chemistry of IVOCs is very poorly understood. This proposal will establish a novel method for quantifying IVOCs in air by using thermal desorption sampling coupled to proton transfer reaction mass spectrometry (TD-PTR-MS). With this approach the total abundance of IVOC alkanes will be measured. The approach will allow a more comprehensive quantification of the IVOC carbon pool by lumping IVOC species into functional groups (i.e., alkanes, cyclic alkanes) or by their molecular weight (i.e. monocyclic aromatics, naphthalenes). The method will be used in a four week field sampling campaign to compare IVOC abundance to volatile organic compound (VOC) abundance measured by PTR-MS and gas chromatography mass spectrometry (GC-MS) to test the proposition that IVOC photooxidation is a major source of urban SOA. Laboratory experiments using a photoreaction reaction chamber will be used to photochemically age diesel fuel and diesel engine exhaust to establish IVOC group reactivity with hydroxyl radical. These experiments will aid the interpretation of field data and enhance the currently sparse knowledge of IVOC lifetimes required for chemical transport modeling. Establishing a measurement method to quantity the abundance of IVOCs in air addresses a critical gap in knowledge of urban air photochemistry and SOA formation.The research will support and train two graduate students and one undergraduate student in analysis and interpretation of organic trace gas. Results and instrumentation used will be incorporated into undergraduate classes and a senior level air quality laboratory class. Research results will be disseminated through conferences and peer reviewed journals. The results will enhance our understanding of the nature and origin of organic compounds in the atmosphere. The public benefit will be a more quantitative understanding of the levels and impacts of diesel engine exhaust in urban air.