Effect of aerosol chemical composition on the photodegradation of nitro-polycyclic aromatic hydrocarbons
Effect of aerosol chemical composition on the photodegradation of nitro-polycyclic aromatic hydrocarbons
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DOI：
10.1021/es990566r
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发表时间：
2000-03-01
影响因子：
11.4
通讯作者：
Nielsen, T
中科院分区：
文献类型：
--
作者：
Feilberg, A;Nielsen, T
研究了四环硝基多环芳烃在大气中的光降解行为，探讨了其在大气中的光降解机理。由有机气溶胶成分引发的光诱导自由基链反应，例如，氧化多环芳烃，是最有可能的主要降解途径颗粒相关的硝基多环芳烃。在模拟柴油机尾气和柴炉烟道气颗粒表面液膜的化学模型系统中研究了光降解速率。在纯溶液（直接光解）和存在不同类别的有机气溶胶成分，包括多环芳烃，羟基多环芳烃，取代苯酚，苯甲醛，和氧多环芳烃（包括多环芳香醌）（间接光解）的相对速率。后四种化合物类的成员被证明可以加速光降解速率。提出的机制来解释这些影响，包括自由基链反应和光诱导的氢提取硝基多环芳烃。多环芳烃是已知的单线态O-2的敏化剂没有加速衰变。某些氧多环芳烃强烈加速硝基多环芳烃的衰变，而其他则没有影响。这种差异与oxy-PAM的激发态的性质和引发自由基链反应的能力有关。模型系统的相关性和环境影响的结果进行了讨论，并与烟雾室研究相同的化合物的相对降解率的结果进行了比较。
The photodegradation of four ring nitro-PAHs in the presence of organic aerosol constituents has been investigated in model systems to determine their degradation mechanism under ambient air conditions. Light-induced radical chain reactions initiated by organic aerosol constituents, e.g., oxy-PAHs, is most likely to be the dominant degradation pathway for particle-associated nitro-PAH. The photodegradation rates were investigated in a chemical model system simulating the liquid film on particles from diesel exhaust and wood stove stack gases. Relative rates were obtained in pure solutions (direct photolysis) and in the presence of different classes of organic aerosol components comprising PAHs, hydroxy-PAHs, substituted phenols, benzaldehydes, and oxy-PAHs (including polycyclic aromatic quinones) (indirect photolysis). Members of the four latter compound classes are demonstrated to accelerate the photodegradation rate. The mechanisms proposed to explain these effects include both radical chain reactions and photoinduced hydrogen abstraction by nitro-PAHs. PAHs that are known sensitizers of singlet O-2 did not accelerate the decay. Certain oxy-PAHs strongly accelerate the nitro-PAH decay, whereas others have no effect. This difference is related to the nature of the excited state of the oxy-PAM and the ability to initiate radical chain reactions. The relevance of the model system and the environmental implications of the results are discussed, and the results are compared with relative degradation rates from smog chamber studies with the same compounds.