Investigation of the photo-oxidation of benzaldehyde and hydroxylated aromatic compounds: application of laser ionization mass spectrometry

众所周知，芳烃（AH）、苯、甲苯和二甲苯异构体（BTX）的气相光氧化导致二次有机气溶胶（SOA）的形成。虽然主要的反应步骤已经被深入研究，但导致化合物最终产生SOA的次级和后续反应步骤仍然不清楚。有证据表明，进一步氧化的初级环保留产品，例如，芳香醛、酚（单羟基和二羟基取代的）和硝基酚在引发SOA形成中可起重要作用。迄今为止，利用现有的分析技术对初级产品的进一步氧化进行的研究在确定i）主要产品的化学性质和ii）主要气溶胶前体以及气溶胶的化学成分方面仅取得了轻微的成功。本项目的主要目的是，因此，从OH和NO3自由基引发的光氧化的AH氧化中观察到的选定的主要环保留化合物的反应产物的详细调查。研究将在大容量光反应器中进行。除了可用的原位FTIR和GC-MS分析方法外，还将使用新的新型质谱技术监测选定系统的化学演变，该质谱技术基于我们小组最近推出的大气压激光电离（APLI）方法。基于激光的电离方法的应用将用于识别不容易分离或用常规分析技术检测不到的产品。这些研究对于更好地了解芳烃的整体光氧化机制和评估其形成二次有机气溶胶的能力具有根本重要性。预计拟议工作的广泛影响在几个方面都很大。首先，烟雾室研究的结果将大大有助于i）我们对芳香烃（BTX）氧化所涉及的次级过程的理解，ii）它将有助于消除目前大气化学化学模型中固有的许多不确定性，iii）它将提高我们对这些过程在大气中形成气溶胶的潜力的总体理解。其次，本工作将为激光质谱技术的应用提供一个重要的展示平台。三是科学培养涉事博士。学生以及文凭/硕士生将涵盖各种各样的跨学科研究工作。完成博士学位后，他们将为进入工作市场或在大学继续他们的研究工作做好充分准备。

It is well established that the gas phase photo-oxidation of aromatic hydrocarbons (AH), benzene, toluene and the xylene isomers (BTX), leads to formation of secondary organic aerosol (SOA). While the primary reaction steps have been intensively studied, secondary and subsequent reaction steps, which lead to compounds eventually producing SOA, remain obscure. There is evidence that further oxidation of primary ring-retaining products, e.g., aromatic aldehydes, phenols (mono- and dihydroxy substituted), and nitrophenols, could play an important role in the initiation of SOA formation. To date studies on the further oxidation of the primary products using the available analytical techniques have only been marginally successful in identifying i) the chemical nature of the main products and ii) the main aerosol precursors as well as the chemical composition of the aerosol. The main aim of this project is, therefore, a detailed investigation of the reaction products from the OH and NO3radical initiated photo-oxidation of selected primary ring-retaining compounds observed in the oxidation of AH. The investigations will be performed in large volume photoreactors. In addition to available in situ FTIR und GC-MS analytical methods the chemical evolution of selected systems will be monitored using new novel mass spectrometric techniques, which are based on the Atmospheric Pressure Laser Ionization (APLI) method, recently introduced by our group. The application of the laser based ionization methods will serve to identify products which are not easily amendable or not detectable with conventional analytical techniques. Such studies are of fundamental importance for obtaining a better Benter/Barnes POXSA general understanding of the overall photo-oxidation mechanism of aromatic hydrocarbons and assessing their ability to form secondary organic aerosol. The broader impact of the proposed work is expected to be high in several regards. First, the results from the smog-chamber studies will contribute significantly i) to our understanding of the secondary processes involved in the oxidation of aromatic hydrocarbons (BTX), ii) it will help to remove many of the uncertainties currently inherent in chemical models of atmospheric chemistry and iii) it will improve our general understanding of the potential of these processes to form aerosol in the atmosphere. Second, the work will provide and an important platform for demonstrating the laser based mass spectrometric techniques which will be applied. Third, the scientific training of the involved Ph.D. students as well as Diploma/Masters students will encompass a broad variety of interdisciplinary research work. After completion of their Ph.D. thesis they will be well prepared for either entering the work market, or continuing their research work at the university level.