DISSOVLED ORGANIC MATTER CONTAINS PREVIOUSLY UNIDENTIFIED FLUOROPHORES IN OLD WOMAN CREEK

Dissolved organic matter (DOM) constitutes a significant carbon pool in the global carbon cycle and is influential in many other processes e.g., altering the fate of contaminants, acting as redox and pH buffers, etc. DOM in the aqueous environment originates from sources ranging from autochthonous (microbial) to allochthonous (terrestrial) precursors. The source of the DOM dictates its composition, which in turn impacts its reactivity in the environment. The isolation of DOM from natural waters is a common practice to preserve and concentrate DOM, yet the extraction method may significantly alter its composition. This study explores the characteristics of DOM collected from Old Woman Creek (OWC) National Estuarine Research Reserve, located in Huron, Ohio, isolated using PPL solid phase extraction (SPE). Previous DOM extraction methods such as C-18 or XAD-8 are limited to hydrophobic compounds, while the novel PPL SPE cartridges capture more polar and non-polar components. PPL and previously collected XAD-8 isolated OWC DOM was characterized using fluorescence spectroscopy. Fluorescence analysis revealed protein-like components not present in previously collected XAD-8 isolated OWC DOM, demonstrating the significance of extraction method on the composition and potential reactivity of isolated DOM. Further analysis corresponded with Diane McKnight’s Fluorescence Index (FI), suggesting microbial DOM is greater than 1.4 and terrestrial DOM is less than 1.4, while OWC DOM represents an ideal intermediate at roughly 1.4.