Session: Aquatic Photochemistry:

Studies that further our understanding of the global carbon cycle allow for more reliable predictions of carbon fluxes that affect our environment and ultimately our climate. Terrestrial organic matter is an important contributor to the global carbon cycle, yet once exported into the oceans as natural organic matter (NOM) continues to elude a definitive fate. An analytically challenging material, studies of terrestrial NOM often include further processing. This processing however may remove compounds indicative of its origin or include microbial populations that may dimmish the role of photochemical transformation. In this study, our approach is to determine how photochemical transformations affect terrestrial material, such as lignin, through the use of a lignin biomarker - vanillin. To this end, vanillin was photo-irradiated at increasing hours of simulated sunlight and a sample collected at different timepoints. Comprehensive analysis was achieved by measuring carbon loss, evaluating the molecular and structural changes using ESI-FT-ICR-MS and proton NMR, and performing ultraviolet-visible and fluorescence spectroscopic analyses to study the optical properties of the photo-produced molecules. A portion of vanillin was extensively transformed into molecules that are similar to those found in marine environments. Additionally, some of the photo-produced molecules have characteristics belonging to carboxyl-rich alicyclic molecules (CRAM) and non-autochthonous molecules. Results from this study indicate the photochemical coupling of terrestrial and marine organic matter and further enhance our understanding of relations between the soil, riverine, and marine carbon cycles.

Dr. Aleksandar I Goranov

Postdoctoral Researcher, Old Dominion University

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