Department of Chemistry, University of Toronto , Toronto, Canada.
Environ Sci Technol. 2013 Nov 19;47(22):12819-26. doi: 10.1021/es402687w. Epub 2013 Nov 5.
In the atmosphere, volatile organic compounds such as glyoxal can partition into aqueous droplets containing significant levels of inorganic salts. Upon droplet evaporation, both the organics and inorganic ions become highly concentrated, accelerating reactions between them. To demonstrate this process, we investigated the formation of organo-nitrogen and light absorbing materials in evaporating droplets containing glyoxal and different ammonium salts including (NH4)2SO4, NH4NO3, and NH4Cl. Our results demonstrate that evaporating glyoxal-(NH4)2SO4 droplets produce light absorbing species on a time scale of seconds, which is orders of magnitude faster than observed in bulk solutions. Using aerosol mass spectrometry, we show that particle-phase organics with high N:C ratios were formed when ammonium salts were used, and that the presence of sulfate ions promoted this chemistry. Since sulfate can also significantly enhance the Henry's law partitioning of glyoxal, our results highlight the atmospheric importance of such inorganic-organic interactions in aqueous phase aerosol chemistry.
在大气中，挥发性有机化合物（如乙二醛）可以分配到含有大量无机盐的水相中。当液滴蒸发时，有机物和无机离子都会高度浓缩，从而加速它们之间的反应。为了证明这一过程，我们研究了含有乙二醛和不同铵盐（包括(NH4)2SO4、NH4NO3 和 NH4Cl）的蒸发液滴中有机氮和吸光物质的形成。我们的结果表明，蒸发乙二醛-（NH4）2SO4 液滴会在几秒钟的时间内产生吸光物质，这比在体相溶液中观察到的速度快几个数量级。使用气溶胶质谱法，我们表明当使用铵盐时会形成具有高 N:C 比的颗粒相有机物，并且硫酸根离子的存在促进了这种化学作用。由于硫酸盐也可以显著增强乙二醛的亨利定律分配，因此我们的结果突出了这种无机-有机相互作用在水相气溶胶化学中的大气重要性。
