Bejan Iustinian, Abd-el-Aal Yasin, Barnes Ian, Benter Thorsten, Bohn Birger, Wiesen Peter, Kleffmann Jörg
Physikalische Chemie/FB C, Bergische Universität Wuppertal, 42097, Wuppertal, Germany.
Phys Chem Chem Phys. 2006 May 7;8(17):2028-35. doi: 10.1039/b516590c. Epub 2006 Mar 20.
Formation of nitrous acid (HONO) in the gas phase has been observed for the first time in a flow tube photoreactor upon irradiation (lambda = 300-500 nm) of 2-nitrophenol and methyl substituted derivatives using a selective and sensitive instrument (LOPAP) for the detection of HONO. Formation of HONO by heterogeneous NO2 photochemistry has been excluded, since production of NO2 under the experimental conditions is negligible. Variation of the surface to volume ratio and the nitrophenol concentration showed that the photolysis occurred in the gas phase indicating that HONO formation is initiated by intramolecular hydrogen transfer from the phenolic OH group to the nitro group. From the measured linear dependence of the HONO formation rate on the reactant's concentration and photolysis light intensity, a non-negligible new HONO source is proposed for the urban atmosphere during the day. Unexpectedly high HONO mixing ratios have been observed recently in several field campaigns during the day. It is proposed that the photolysis of aromatic compounds containing the ortho-nitrophenol entity could help to explain, at least in part, this high contribution of HONO to the oxidation capacity of the urban atmosphere.
在流动管光反应器中，首次观察到在使用用于检测亚硝酸（HONO）的选择性灵敏仪器（长路径吸收光度计，LOPAP）对2-硝基苯酚及其甲基取代衍生物进行波长为300 - 500 nm的辐照时，气相中亚硝酸（HONO）的形成。由于在实验条件下二氧化氮（NO₂）的生成量可忽略不计，因此排除了通过非均相NO₂光化学形成HONO的情况。表面体积比和硝基苯酚浓度的变化表明光解发生在气相中，这表明HONO的形成是由酚羟基向硝基的分子内氢转移引发的。根据测得的HONO形成速率与反应物浓度和光解光强度的线性关系，提出在白天城市大气中存在一个不可忽略的新HONO来源。最近在几次野外实验中，白天观测到了意外高的HONO混合比。有人提出，含有邻硝基苯酚基团的芳香化合物的光解至少可以部分解释HONO对城市大气氧化能力的这种高贡献。
