Atmospheric aerosol, solid particles or liquid droplets suspended in a gas, contain carbonyl compounds that can react with amines or ammonia to produce brown carbon. Brown carbon is near-UV light absorbing organic carbon that appears brown to yellow in color. These carbon compounds have been found to contribute to positive radiative forcing, raising global warming concerns. Here, atmospheric aerosol mimics of the carbonyls glyoxal and glycolaldehyde, and the nitrogen source ammonium sulfate, are of interest. The mimics consisted of 50 mM solutions of varying carbonyl ratios and a constant amount of ammonium sulfate, and were analyzed with supercritical fluid chromatography mass spectrometry and UV-Visible spectroscopy. Both analyses revealed that changing the ratio of carbonyls changes the type and abundance of brown carbon products. UV-Visible analysis suggests that more light absorbing products are formed when there is a nearly equal ratio of glyoxal and glycolaldehyde in the system. Mass spectrometry analysis identified various product trends in regards to the abundance of product as the amount of glyoxal in the system increases. Further work, including fragmentation and <sup>15</sup>N isotopic experiments, is needed to determine structures and mechanisms to explain the observed trends.

Product trend analysis and light absorption of atmospheric aerosol mimics

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.