AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Photosensitized Processes as an Alternative Photochemical Pathways in the Atmospheric Bulk Aqueous Phase
MAJDA MEKIC, Wei Deng, Wei Song, Xinming Wang, Xiang Ding, Sasho Gligorovski, Guangzhou Institute of Geochemistry, CAS
Abstract Number: 424 Working Group: There Must be Something in the Water: Cloud, Fog and Aerosol Aqueous Chemistry for Aerosol Production
Abstract Dicarboxylic acids are ubiquitous water-soluble organic compounds that have been detected in atmospheric aerosols, cloud water and rainwaters. Photolysis and oxidation by atmospheric oxidants such as hydroxyl radical (OH) play an important role in controlling the concentrations of dicarboxylic acids in the atmospheric aqueous phase.
In addition to direct photolysis and oxidation processes, degradation of dicarboxylic acids can also occur by indirect photolysis or photosensitized process. In this study, the importance of atmospheric photosensitization is evaluated in bulk aqueous solution. Irradiation experiments in aqueous solution indicate that excited triplet state of pyruvic acid is able to photosensitize the degradation of other dicarboxylic acids. The effect of ionic strength on the photosensitization was evaluated.
Moreover, laboratory batch experiments suggest that the photosensitized process toward dicarboxylic acids could be a relevant source of oligomers (e.g. HULIS (HUmic Like Substances)). In this study oligomers were analyzed using high-resolution linear ion trap Orbitrap mass spectrometer which can deliver high resolving power and mass accuracy. This analytical technique allowed to suggest the unambiguous composition of formed molecules during the photosensitized process as data were gathered in the range between m/z 50 and m/z 2000 amu. Typical regular patterns of oligomer formation were observed, and extended up to 1200 amu.
The present findings strongly suggest that photosensitized degradation of dicarboxylic acids in atmospheric aqueous phase may be an effective degradation pathway in comparison to their removal induced by OH radical and direct photolysis processes.