As a complex mixture containing a multitude of components with varied composition and reactivity, dissolved organic matter (DOM) could regulate the retention of uranium (U) by soil solids, thus decreasing mobility and bioavailability of U. However, the complexation of U by DOM can also release of U from solids to the soil solution. Thus increase in soil DOM concentrations would lead to an increased potential for U-ligand interactions, which would increase the mobilization of U. Additionally, changes in the composition of DOM, rather than total concentration, may also alter U mobility. Thus the chemical composition and characterization of DOM can provide insight into the reactivity of DOM in the environment.<br/>The primary objective of this study is to identify the key organic molecules that facilitate U mobilization during various stages of leaf litter decomposition using a lab-scale decomposition and column leaching experiment. The dissolution of U being significantly enhanced in the presence of leachate collected after 48 hours of incubation comparison to the leachate collected at later harvesting points (~10 fold). Further, we conducted a more accurate compound classification for litter leachate analyzed by high-resolution spectroscopy based on an assessment of the C/H/O/N/P stoichiometric ratio of over 15000 elemental formulas of compound classified in 6 major categories. The leachate at an early stage of decomposition had 1) higher number of organic compounds 2) more CHO and CHON compounds (which likely provide extra binding sites for radionuclide contaminants) and 3) more heteroatoms (N, S and P), thus more hydrophilic that may promote U binding. This study showed that not only the amount but also the molecular characteristics of OM might, in part, be responsible for the enhanced mobilization of U in soil. These findings have implications on the long-term management of contaminated sites.<br/> <br/>

Chemical characterization of dissolved organic matter originating from decomposing leaf to elucidate their differential ability to influence the mobilization of uranium from stable mineral form

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.