Role of Water Molecule in the Gas-Phase Formation Process of Nitrated Polycyclic Aromatic Hydrocarbons in the Atmosphere: A Computational Study
Role of Water Molecule in the Gas-Phase Formation Process of Nitrated Polycyclic Aromatic Hydrocarbons in the Atmosphere: A Computational Study
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水分子在大气中硝化多环芳烃气相形成过程中的作用：计算研究
DOI：
10.1021/es500453g
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发表时间：
2014
影响因子：
11.4
通讯作者：
Wang Wenxing
中科院分区：
文献类型：
--
作者：
Zhang Qingzhu;Gao Rui;Xu Fei;Zhou Qin;Jiang Guibin;Wang Tao;Chen Jianmin;Hu Jingtian;Jiang Wei;Wang Wenxing
硝基多环芳烃因其高度的直接致突变性和致癌性而成为全球范围内令人担忧的空气污染物。从机理上了解其形成过程对于成功地防止其大气污染至关重要。在这里，硝基多环芳烃的形成所产生的OH引发和NO3引发的大气反应的多环芳烃的使用量子化学计算进行了研究。人们普遍认为OH或NO3自由基攻击PAH分子中芳环的C原子，然后NO2与OH-PAH或NO3-PAH加成物在邻位加成，失去水或硝酸生成硝基多环芳烃。然而，计算表明，从OH-NO2-PAH加合物通过单分子分解的直接损失的水是积极不利的。本研究首次揭示了水分子在OH-NO2-PAH加合物失水过程中起着重要的催化作用，促进了硝基多环芳烃的生成。此外，水的引入还通过NO2与OH-PAH或NO3-PAH的对位加成，打开了新的生成途径。利用Rice-Ramsperger-Kassel-Marcus（RRKM）理论推导了多环芳烃与OH和NO3自由基加成反应的单个和总速率常数。
Nitro-PAHs are globally worrisome air pollutants because their high direct-acting mutagenicity and carcinogenicity. A mechanistic understanding of their formation is of crucial importance for successful prevention of their atmospheric pollution. Here, the formation of nitro-PAHs arising from the OH-initiated and NO3-initiated atmospheric reactions of PAHs was investigated by using quantum chemical calculations. It is widely assumed that OH or NO3radicals attack on the C atoms of the aromatic rings in the PAH molecule, followed by the addition of NO2to the OH–PAH or NO3–PAH adducts at theorthoposition and the loss of water or nitric acid to form nitro-PAHs. However, calculations show that the direct loss of water from the OH–NO2–PAH adducts via the unimolecular decomposition is energetically unfavorable. This study reveals for the first time that water molecule plays an important catalytic effect on the loss of water from the OH–NO2–PAH adducts and promotes the formation of nitro-PAHs. In addition, the introduction of water unwraps new formation pathway through the addition of NO2to the OH–PAH or NO3–PAH adduct at theparaposition. The individual and overall rate constants for the addition reactions of PAHs with OH and NO3radicals were deduced by using the Rice–Ramsperger–Kassel–Marcus (RRKM) theory.