Investigation of PAH Photodegradation in Solutions

描述（由申请人提供）：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，增加了环境中这些化合物的总丰度。半挥发性多环芳烃被细颗粒物吸附后通过吸入进入人体。了解多环芳烃释放到环境后的命运关系到公共卫生。日光诱导光氧化是去除环境中多环芳烃的重要方法。提出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变速率。与以往的研究不同，本研究的结果可用于识别和量化局部环境中的多环芳烃光氧化产物。这是一个重要的信息，因为多环芳烃光氧化产物不仅比多环芳烃和另一组疑似致癌物反应性更强，而且更容易溶于水系统，因此可以长距离运输。

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.