Cory, R. M., University of Minnesota, St. Paul, USA, cory@chem.umn.edu
McNeill, K. ., University of Minnesota, Minneapolis, USA, mcneill@chem.umn.edu
Cotner, J. B., University of Minnesota, St. Paul, USA, cotne002@umn.edu

SINGLET OXYGEN UPTAKE BY AQUATIC FULVIC ACID LEADS TO PRODUCTION OF HYDROGEN PEROXIDE AND OXIDIZED ORGANIC COMPOUNDS

Singlet oxygen (1O2, 1Δg) is a reactive oxygen species produced by the interaction between photo-excited dissolved organic matter (DOM) and dissolved oxygen. Singlet oxygen is capable of oxidizing several compound classes that comprise DOM and thus may play a role in photochemical transformations of DOM. We studied the uptake of 1O2 by Suwannee River and Pony Lake fulvic acids, the terrestrial and microbial end-member aquatic humic substances, respectively. Labeling experiments (18O2) demonstrated that 1O2 is involved in the photochemical weathering of fulvic acids, yielding both stable oxidized products as well as hydrogen peroxide (H2O2). Our results suggest that at DOM concentrations measured in freshwaters (1-100 mg-C L-1), the 1O2 pathway accounts for <1 to > 50% of the total H2O2 formed photochemically by the fulvic acid fraction of DOM. Employing the van Krevelen approach to ultra-high resolution mass spectrometry analysis of the fulvic acids revealed that lignin-like compounds were the preferred 1O2-substrate for Suwannee River fulvic acid. For Pony Lake fulvic acid, 1O2 preferentially reacted with relatively saturated compounds low in oxygen.

Oral presentation

Presentation is given by student: No
Session #:SS01
Date: Friday, June 13, 2008
Time: 2:15 PM

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