Department of Chemistry, Harvey Mudd College , 301 Platt Boulevard, Claremont, California 91711, United States.
Department of Chemistry and Biochemistry, University of San Diego , 5998 Alcala Park, San Diego California 92110, United States.
Environ Sci Technol. 2016 Jul 19;50(14):7443-52. doi: 10.1021/acs.est.6b00909. Epub 2016 Jun 30.
The reported optical, physical, and chemical properties of aqueous Maillard reaction mixtures of small aldehydes (glyoxal, methylglyoxal, and glycolaldehyde) with ammonium sulfate and amines are compared with those of aqueous extracts of ambient aerosol (water-soluble organic carbon, WSOC) and the humic-like substances (HULIS) fraction of WSOC. Using a combination of new and previously published measurements, we examine fluorescence, X-ray absorbance, UV/vis, and IR spectra, complex refractive indices, (1)H and (13)C NMR spectra, thermograms, aerosol and electrospray ionization mass spectra, surface activity, and hygroscopicity. Atmospheric WSOC and HULIS encompass a range of properties, but in almost every case aqueous aldehyde-amine reaction mixtures are squarely within this range. Notable exceptions are the higher UV/visible absorbance wavelength dependence (Angström coefficients) observed for methylglyoxal reaction mixtures, the lack of surface activity of glyoxal reaction mixtures, and the higher N/C ratios of aldehyde-amine reaction products relative to atmospheric WSOC and HULIS extracts. The overall optical, physical, and chemical similarities are consistent with, but not demonstrative of, Maillard chemistry being a significant secondary source of atmospheric HULIS. However, the higher N/C ratios of aldehyde-amine reaction products limits the source strength to ≤50% of atmospheric HULIS, assuming that other sources of HULIS incorporate only negligible quantities of nitrogen.
报告了小醛（乙二醛、甲基乙二醛和甘油醛）与硫酸铵和胺的水合美拉德反应混合物的光学、物理和化学性质，并将其与大气气溶胶的水提取物（水溶性有机碳，WSOC）和 WSOC 的腐殖质样物质（HULIS）部分进行了比较。利用新的和以前发表的测量结果的组合，我们研究了荧光、X 射线吸收、紫外/可见和红外光谱、复折射率、（1）H 和（13）C NMR 光谱、热图、气溶胶和电喷雾电离质谱、表面活性和吸湿性。大气 WSOC 和 HULIS 涵盖了一系列性质，但在几乎所有情况下，醛-胺反应混合物都完全在这个范围内。值得注意的例外是观察到甲基乙二醛反应混合物的更高的紫外/可见吸收波长依赖性（Angström 系数），乙二醛反应混合物缺乏表面活性，以及与大气 WSOC 和 HULIS 提取物相比，醛-胺反应产物的 N/C 比值较高。整体光学、物理和化学相似性表明美拉德化学是大气 HULIS 的一个重要次生来源，但并非确凿证据。然而，醛-胺反应产物的较高 N/C 比值限制了源强度≤大气 HULIS 的 50%，假设 HULIS 的其他来源只包含可忽略不计的氮量。
