Al-Abadleh Hind A, Motaghedi Fatemeh, Mohammed Wisam, Rana Md Sohel, Malek Kotiba A, Rastogi Dewansh, Asa-Awuku Akua A, Guzman Marcelo I
Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada.
Department of Chemistry, University of Kentucky, Kentucky, 40506, USA.
Commun Chem. 2022 Sep 19;5(1):112. doi: 10.1038/s42004-022-00732-1.
Nitrogen-containing organic carbon (NOC) in atmospheric particles is an important class of brown carbon (BrC). Redox active NOC like aminophenols received little attention in their ability to form BrC. Here we show that iron can catalyze dark oxidative oligomerization of o- and p-aminophenols under simulated aerosol and cloud conditions (pH 1-7, and ionic strength 0.01-1 M). Homogeneous aqueous phase reactions were conducted using soluble Fe(III), where particle growth/agglomeration were monitored using dynamic light scattering. Mass yield experiments of insoluble soot-like dark brown to black particles were as high as 40%. Hygroscopicity growth factors (κ) of these insoluble products under sub- and super-saturated conditions ranged from 0.4-0.6, higher than that of levoglucosan, a prominent proxy for biomass burning organic aerosol (BBOA). Soluble products analyzed using chromatography and mass spectrometry revealed the formation of ring coupling products of o- and p-aminophenols and their primary oxidation products. Heterogeneous reactions of aminophenol were also conducted using Arizona Test Dust (AZTD) under simulated aging conditions, and showed clear changes to optical properties, morphology, mixing state, and chemical composition. These results highlight the important role of iron redox chemistry in BrC formation under atmospherically relevant conditions.
大气颗粒物中的含氮有机碳（NOC）是棕碳（BrC）的重要类别。像氨基酚这样具有氧化还原活性的NOC在形成BrC的能力方面鲜受关注。在此我们表明，在模拟气溶胶和云的条件下（pH值为1 - 7，离子强度为0.01 - 1 M），铁能够催化邻氨基酚和对氨基酚的暗氧化低聚反应。使用可溶性Fe(III)进行均相水相反应，通过动态光散射监测颗粒生长/团聚情况。不溶性煤烟状深棕色至黑色颗粒的质量产率实验高达40%。这些不溶性产物在亚饱和和过饱和条件下的吸湿性增长因子（κ）范围为0.4 - 0.6，高于左旋葡聚糖（生物质燃烧有机气溶胶（BBOA）的一个重要代表物）。使用色谱法和质谱法分析可溶性产物，揭示了邻氨基酚和对氨基酚的环偶联产物及其初级氧化产物的形成。在模拟老化条件下，还使用亚利桑那测试粉尘（AZTD）进行了氨基酚的非均相反应，结果显示其光学性质、形态、混合状态和化学成分都有明显变化。这些结果突出了铁氧化还原化学在大气相关条件下BrC形成中的重要作用。
