CHARACTERIZATION AND PHOTOREACTIVITY OF CHROMOPHORIC MARINE-DISSOLVED ORGANIC MATTER

David Gonzales1, Michael Rui Clemente Alves1, Duyen Dang1, Kimberly A Prather2 and Vicki H Grassian3, (1)University of California San Diego, Chemistry and Biochemistry, La Jolla, CA, United States, (2)Scripps Institution of Oceanography, La Jolla, CA, United States, (3)University of California San Diego, Chemistry and Biochemistry, La Jolla, United States
Abstract:
Marine-dissolved organic matter (m-DOM) is a diverse assortment of compounds in seawater that includes proteins, fatty acids and aromatics that originate from microbiology and the decay of plant life. Although it has been studied for years, even with high resolution analysis, its composition still remains uncertain. Recently, the chromophoric component within m-DOM has been highlighted as a possible driver for photochemical reactions. When irradiated with solar light, chromophoric m-DOM at the sea surface layer can absorb photons between 280 and 500 nm. Once excited into a singlet state, there is rapid intersystem crossing into a lower energy triplet state which can then react with other organic species, facilitating photochemistry in the marine environment. In this study, bulk sea water has been collected from three bloom cycles in a months long experiment performed in a unique ocean-atmosphere facility at various times to better understand the temporal changes of bulk m-DOM in a marine bloom. The m-DOM was analyzed using heated electrospray ionization Orbitrap mass spectrometry, infrared spectroscopy, and excitation-emission matrix spectroscopy.In this study, we also compared the photoreactivity of m-DOM across a phytoplankton bloom.