Photooxidation of succinic acid with hydrogen peroxide: Changes in hygroscopic behavior
Authors:Shaun Cook, Julie Hofstra, Aaron Ninokawa
Mentor:Paula Hudson, Assistant Professor of Analytical Chemistry, California State University Fullerton
Atmospheric particles (aerosol) have been identified as important factors in understanding climate change based on their ability to act as cloud condensation nuclei (CCN). The extent to which aerosol affect climate is determined, in part, by their hygroscopic properties, how they take up water vapor. A branch of chemical compounds, dicarboxylic acids, are common components of atmospheric aerosol and have vastly different hygroscopic properties depending on the particular composition where some compounds take up water and other do not. Further, the particles can react with various chemicals in the atmosphere producing new products, possibly having different hygroscopic properties than the original particles. In this study, the hygroscopic properties of dicarboxylic acid aerosol were measured with a tandem differential mobility analyzer (TDMA) and compared to reaction products resulting from a light induced oxidation of the dicarboxylic acid. Specifically, the changes in hygroscopic behavior of succinic acid, a dicarboxylic acid with both anthropogenic and natural sources, after undergoing an aqueous phase photo-oxidation (light induced oxidation) with an atmospherically relevant oxidizer, hydrogen peroxide, were studied. Before the oxidation reaction, pure succinic acid is not hygroscopic. In a photolyzed mixture with hydrogen peroxide, hydroxyl radicals are produced which then react with succinic acid to form products that are hygroscopic. The reaction conditions were examined by comparing solutions with varying succinic acid : hydrogen peroxide ratios and light exposure time. Major reaction products were determined with gas chromatography-flame ionization detection (GC-FID). This study provides a framework for future investigations to fully understand and predict the role of chemical reactions in altering atmospheric conditions that affect climate.