Exploring matrix effects on photochemistry of organic aerosols
Exploring matrix effects on photochemistry of organic aerosols
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DOI：
10.1073/pnas.1322106111
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发表时间：
2014-09-23
影响因子：
11.1
通讯作者：
Nizkorodov, Sergey A.
中科院分区：
文献类型：
--
作者：
Lignell, Hanna;Hinks, Mallory L.;Nizkorodov, Sergey A.
本工作探讨了环境对2，4-二硝基苯酚（24-DNP）光解速率的影响，这是一种重要的环境毒素。与24-DNP在水溶液中的缓慢光解形成鲜明对比的是，对于溶解在1-辛醇中或嵌入在由α-蒎烯的臭氧分解产生的次级有机材料（SOM）中的24-DNP，光解速率增加超过一个数量级。降低温度对24-DNP在有机质中的光解速率的影响比24-DNP在正辛醇中的光解速率的影响更为显著，其有效活化能分别为53 kJ/mol和12 kJ/mol。我们讨论的可能性，增加的粘度的SOM矩阵约束的分子运动，从而抑制氢原子转移反应的光激发的24-DNP。这是，据我们所知，第一次报告的矩阵的显着影响，可能的粘度，在SOM内的大气光化学反应的速率。这表明，有机气溶胶中的光化学过程的速率将取决于相对湿度和温度，因此高度。研究结果进一步表明，有机质中的光化学可能在大气有机物的转化中起着关键作用。例如，24-DNP和其他硝基芳族化合物在有机颗粒物中应易于光降解，这对于预测其环境归宿和影响具有重要意义。
This work explores the effect of the environment on the rate of photolysis of 2,4-dinitrophenol (24-DNP), an important environmental toxin. In stark contrast to the slow photolysis of 24-DNP in an aqueous solution, the photolysis rate is increased by more than an order of magnitude for 24-DNP dissolved in 1-octanol or embedded in secondary organic material (SOM) produced by ozonolysis of alpha-pinene. Lowering the temperature decreased the photolysis rate of 24-DNP in SOM much more significantly than that of 24-DNP in octanol, with effective activation energies of 53 kJ/mol and 12 kJ/mol, respectively. We discuss the possibility that the increasing viscosity of the SOM matrix constrains the molecular motion, thereby suppressing the hydrogen atom transfer reaction to the photo-excited 24-DNP. This is, to our knowledge, the first report of a significant effect of the matrix, and possibly viscosity, on the rate of an atmospheric photochemical reaction within SOM. It suggests that rates of photochemical processes in organic aerosols will depend on both relative humidity and temperature and thus altitude. The results further suggest that photochemistry in SOM may play a key role in transformations of atmospheric organics. For example, 24-DNP and other nitro-aromatic compounds should readily photo-degrade in organic particulate matter, which has important consequences for predicting their environmental fates and impacts.