Investigation of PAH Photodegradation in Solutions

描述(申请人提供)：多环芳烃(PAHs)是自然界中普遍存在的致癌和致突变污染物。人类活动，包括化石燃料的燃烧，对环境中这些化合物的总丰度做出了贡献。吸附在细颗粒物中的半挥发性多环芳烃通过吸入进入人体。了解多环芳烃被释放到环境中后的命运是一个公共卫生问题。太阳光诱导光氧化是去除环境中多环芳烃的一种重要方法。这项拟议的研究旨在测量光化学速率常数和产物量子产率，以预测包括大气颗粒、水和其他环境表面在内的凝聚相系统中多环芳烃的衰减速率。与以前的研究不同，这项研究的结果可以用于识别和量化当地环境中的多环芳烃光氧化产物。这是重要的信息，因为多环芳烃的光氧化产物不仅比多环芳烃和另一组可疑的致癌物更具活性，而且它们在水体系中也更易溶解，因此可以传输更长的距离。 拟议工作的假设是，主要通过自由基阳离子介导的机制降解的多环芳烃将具有依赖于其所在介质的电子供体能力的降解速率，并且在这些过程中将产生各种未充分表征和以前未识别的光产物。为了探索这一假设，本研究制定了三个具体的目标：(1)利用结构敏感的高效液相/质谱仪/质谱仪技术表征多环芳烃的光降解产物；(2)测量观察到的光产物在不同极性的溶液中的形成速率和量子产率，以阐明电子供体对环境中多环芳烃光降解速率的作用；(3)在光解过程中操纵特定机理的中间体，以阐明具有一系列电子清除潜力的基质中多环芳烃光降解的主要机理。 这项拟议的工作将使用最近开发的LC/MS/MS技术来测量多环芳烃在溶液中的光氧化产物量子产率，相对于其他分析技术具有特殊的灵敏度和选择性。该项目的成功将有助于阐明环境对吸入颗粒物的破坏性影响所起的作用。这项研究还将提供对环境中多环芳烃的光降解进行建模所需的动力学参数，从而启发人们从受污染的地点移除的想法。

DESCRIPTION (provided by applicant): Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic and mutanogenic pollutants ubiquitous in the natural world. Human activities, including the combustion of fossil fuels, contribute to the total abundance of these compounds in the environment. Semi-volatile PAHs adsorbed to fine particulate matter enter the body via inhalation. It is a matter of public health to understand the fate of PAHs after they are released into the environment. Sunlight-induced photooxidation is an important method of PAH removal from the environment. The proposed research is designed to measure photochemical rate constants and product quantum yields necessary to predict the rates of PAH decay in condensed phase systems including atmospheric particles, water, and other environmental surfaces. Unlike previous studies, the results of this study can be used to identify and quantify PAH photooxidation products in local environments. This is important information because PAH photooxidation products are not only more reactive than PAHs and another group of suspected carcinogens, but they are also more soluble in aqueous systems and consequently can be transported over longer distances. The hypothesis of the proposed work is that PAHs that degrade predominately via the radical-cation mediated mechanism will have degradation rates that are dependent on the electron-donor capacity of the media in which they reside, and there will be a diversity of under-characterized and previously unidentified photoproducts created in these processes. To explore this hypothesis, three specific objectives for the proposed research have been formulated: (1) Characterize photoproducts of PAH photodegradation using structurally sensitive HPLC/MS/MS techniques; (2) Measure formation rates and quantum yields of the observed photoproducts in solutions with varied polarity to elucidate the role of electron donors on the rates of PAH photodegradation in the environment; (3) Manipulate mechanism-specific intermediates during photolysis to elucidate the dominant mechanism for PAH photodegradation in matrices with a range of electron-scavenging potentials. The proposed work will use recently developed LC/MS/MS techniques to measure the product quantum yields of PAH photooxidation in solutions with exceptional sensitivity and selectivity relative to other analytical techniques. The success of this project will help to elucidate the role of the environment on the damaging effects of particle inhalation. The study will also provide kinetic parameters necessary to model the photodegradation of environmental PAHs, inspiring ideas for removal from contaminated sites.