Analyzing the Photochemistry of Dissolved Organic Material In Leaf Leachate Samples Using Fluorescence and X-Ray Spectroscopy

Abstract

Dissolved organic material (DOM) in inland water sources is produced by decomposing terrestrial organic material by aquatic life and sunlight. The degradation of these materials can produce carbon byproducts such as CO2 and inorganic carbons. Yet, the photochemical breakdown of DOM is scarcely explored, and not much is known about the functional groups present in compounds produced by sunlight exposure. Previous studies on this topic have employed Mass and UV-Vis spectrometry to examine the effects of irradiation on DOM samples; however, because of the limited use of these methods and the extreme nature of DOM composition, not much besides the presence of aromatics and aliphatics has been determined. In this study, we use X-Ray Absorption Near-Edge Structure (XANES) spectroscopy and Excitation-Emission Matrix (EEM) spectroscopy to analyze the composition of leaf leachate samples created from leaf litter collected from the New Jersey Pine Barrens. Two leachate samples were made with litter of different decomposition stages. With EEM analysis, we were able to identify photo-produced compounds in the B and T Coble Peak regions and photo-liable compounds in the C Coble peak region. XANES confirmed the presence of phenols, carboxylic acids, and indoles present in irradiated samples.