Department of Molecular Engineering, Kyoto University, Kyoto 615-8510, Japan.
Phys Chem Chem Phys. 2011 Mar 21;13(11):5144-9. doi: 10.1039/c0cp01497d. Epub 2011 Jan 31.
The hydrolytic disproportionation of gaseous NO(2) on water's surface (2 NO(2) + H(2)O → HONO + NO(3)(-) + H(+)) (R1) has long been deemed to play a key, albeit unquantifiable role in tropospheric chemistry. We recently found that (R1) is dramatically accelerated by anions in experiments performed on aqueous microjets monitored by online electrospray mass spectrometry. This finding let us rationalize unresolved discrepancies among previous laboratory results and suggested that under realistic environmental conditions (R1) should be affected by everpresent surfactants. Herein, we report that NO(2)(g) uptake is significantly enhanced by cationic surfactants, weakly inhibited by fulvic acid (FA, a natural polycarboxylic acid) and anionic surfactants, and unaffected by 1-octanol. Surfactants appear to modulate interfacial anion coverage via electrostatic interactions with charged headgroups. We show that (R1) should be the dominant mechanism for the heterogeneous conversion of NO(2)(g) to HONO under typical atmospheric conditions throughout the day. The photoinduced reduction of NO(2) into HONO on airborne soot might play a limited role during daytime.
气态 NO(2)在水面上的水解歧化作用（2 NO(2) + H(2)O → HONO + NO(3)(-) + H(+））（R1）长期以来一直被认为在对流层化学中起着关键作用，尽管无法量化。我们最近在通过在线电喷雾质谱监测的水微射流实验中发现，（R1）被阴离子显著加速。这一发现使我们能够合理地解释先前实验室结果之间存在的未解决的差异，并表明在实际环境条件下，（R1）应该受到一直存在的表面活性剂的影响。在此，我们报告气态 NO(2)的吸收明显被阳离子表面活性剂增强，被富里酸（FA，一种天然多羧酸）和阴离子表面活性剂弱抑制，不受 1-辛醇影响。表面活性剂似乎通过与带电头基的静电相互作用来调节界面阴离子覆盖。我们表明，（R1）应该是在整个白天典型大气条件下气态 NO(2)异相转化为 HONO 的主要机制。空气中烟尘的光诱导将 NO(2)还原成 HONO，在白天可能作用有限。
