Tropospheric aerosol directly affect the earth's climate by reflecting and scattering incoming solar radiation, and indirectly by acting as cloud condensation nuclei (CCN). Low molecular weight a,?-dicarboxylic acids represent a fraction of these aerosol, one of which is succinic acid (SA), a C4 dicarboxylic acid. Although SA does not act as a CCN due to its low hygroscopicity, oxidation reactions result in products that are hygroscopic and can better act as CCN. To improve our understanding of the oxidation pathways, we conducted aqueous photochemical reactions of SA and hydroxyl radicals, an atmospheric oxidizer, that was produced from the photolysis of hydrogen peroxide (H2O2). In the absence of H2O2, decarboxylation followed by radical mediated termination led to the formation of adipic acid, a C6 dicarboxylic acid. At low H2O2 concentrations, H2O2:SA between ratios of 1:8 and 2:1, reaction intermediates began to recombine in radical mediated termination steps which led to the formation of tricarballylic acid, 1,2,4-butanetricarboxylic acid, and 1,2,3,4-butanetetracarboxylic acid, C6, C7, and C8 polycarboxylic acids. When the H2O2:SA ratio was 5:1 and 10:1, photooxidation took precedence over other photochemical reaction pathways. Succinic acid reacted to form malonic acid, a C3 dicarboxylic acid, which then further oxidized to form oxalic acid, a C2 dicarboxylic acid. This study provides an insight on some of the photochemical reactions of SA that take place in the atmosphere, and demonstrates the effect they can have on climate change.

Oxidation reaction pathways of succinic acid in the aqueous phase

246th National Meeting (2013)

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