Brown Carbon Formation by Aqueous-Phase Carbonyl Compound Reactions with Amines and Ammonium Sulfate

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• 作者：Michelle H. Powelson ; Brenna M. Espelien ; Lelia N. Hawkins ; Melissa M. Galloway ; David O. De Haan
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：January 21, 2014
• 年：2014
• 卷：48
• 期：2
• 页码：985-993
• 全文大小：495K
• ISSN：1520-5851

文摘

Reactions between small water-soluble carbonyl compounds, ammonium sulfate (AS), and/or amines were evaluated for their ability to form light-absorbing species in aqueous aerosol. Aerosol chemistry was simulated with bulk phase reactions at pH 4, 275 K, initial concentrations of 0.05 to 0.25 M, and UV鈥搗is and fluorescence spectroscopy monitoring. Glycolaldehyde鈥揼lycine mixtures produced the most intense absorbance. In carbonyl compound reactions with AS, methylamine, or AS/glycine mixtures, product absorbance followed the order methylglyoxal > glyoxal > glycolaldehyde > hydroxyacetone. Absorbance extended into the visible, with a wavelength dependence fit by absorption 脜ngstrom coefficients (脜_abs) of 2 to 11, overlapping the 脜_abs range of atmospheric, water-soluble brown carbon. Many reaction products absorbing between 300 and 400 nm were strongly fluorescent. On a per mole basis, amines are much more effective than AS at producing brown carbon. In addition, methylglyoxal and glyoxal produced more light-absorbing products in reactions with a 5:1 AS-glycine mixture than with AS or glycine alone, illustrating the importance of both organic and inorganic nitrogen in brown carbon formation. Through comparison to biomass burning aerosol, we place an upper limit on the contribution of these aqueous carbonyl鈥揂S鈥揳mine reactions of 鈮?0% of global light absorption by brown carbon.