Atmospheric aerosol that contain brown carbon (BrC) can absorb light from the sun and release the energy as heat back onto our earth, contributing to global warming. The absorbance and products of BrC-containing compounds were analyzed before and after exposure to UV light. These BrC-containing compounds were formed from the aqueous  reactions of the organic carbonyl compounds methylglyoxal (MG), glyoxal (GX), glycolaldehyde (GD), and hydroxyacetone (HX), with ammonium sulfate (AS). Each carbonyl + AS system absorbs light within both the UV and the visible light range, and decreases in absorbance indicate the breaking apart of the BrC species. Photolysis rates followed a first order trend for all compounds except GX + AS, which suggests that a single carbonyl + AS system cannot be used as a proxy for true BrC species behavior. Using supercritical fluid chromatography-electrospray ionization-mass spectrometry, masses that decreased or disappeared during photolysis were identified, and structures for many of these were determined. Proposed structures were confirmed more strongly with fragmentation data.

Comparison of photolysis rate constants and identification of products in aqueous atmospheric aerosol mimics

2019 Spring National Meeting

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