The Effect Of Temperature On The Quantum Yield Of Photochemical Hydroxyl Radical Production From Dissolved Organic Matter
McKay, Garrett 1 ; Rosario-Ortiz, Fernando L 2
1 University of Colorado-Boulder
2 Â鶹Ãâ·Ñ°æÏÂÔØ
Photochemical processes in natural waters are central to carbon cycling, biological processes, and the fate of anthropogenic organic pollutants. For example, the production of singlet oxygen, hydroxyl radical (?OH), and triplet-excited states from DOM photolysis has been shown to degrade a variety of organic chemicals in natural waters. Calculation of pollutant degradation rates in these systems relies on the apparent quantum yield (Φ) for the formation of these reactive intermediates. However, there has yet to be an assessment of the temperature dependence of Φ over environmentally relevant temperatures. Thus, we have measured the temperature-dependence of Φ for ?OH for a set of DOM standards, with and without added catalase (used to decompose H2O2), giving a range of Arrhenius activation energies of 16-32 kJ/mol. p-Benzoquinone was used as a model sensitizer as a comparison to DOM. This presentation will discuss these data and the mechanistic and practical applications to environmental photochemistry.