Photoproduction of hydrogen peroxide in aqueous solution from model compounds for chromophoric dissolved organic matter (CDOM).
To explore whether quinone moieties are important in chromophoric dissolved organic matter (CDOM) photochemistry in natural waters, hydrogen peroxide (H2O2) production and associated optical property changes were measured in aqueous solutions irradiated with a Xenon lamp for CDOM model compounds (dihydroquinone, benzoquinone, anthraquinone, napthoquinone, ubiquinone, humic acid HA, fulvic acid FA). All compounds produced H2O2 with concentrations ranging from 15 to 500 μM. Production rates were higher for HA vs. FA (1.32 vs. 0.176 mM h(-1)); values ranged from 6.99 to 0.137 mM h(-1) for quinones. Apparent quantum yields (Θ app; measure of photochemical production efficiency) were higher for HA vs. FA (0.113 vs. 0.016) and ranged from 0.0018 to 0.083 for quinones. Dihydroquinone, the reduced form of benzoquinone, had a higher production rate and efficiency than its oxidized form. Post-irradiation, quinone compounds had absorption spectra similar to HA and FA and 3D-excitation-emission matrix fluorescence spectra (EEMs) with fluorescent peaks in regions associated with CDOM.
School of Earth and Environmental Sciences, Schmid College of Science and Technology, Chapman University, Orange, CA 92866, United States.
Catherine D
CD
Clark
School of Earth and Environmental Sciences, Schmid College of Science and Technology, Chapman University, Orange, CA 92866, United States. Electronic address: debruyn@chapman.edu.
Warren
W
de Bruyn
School of Earth and Environmental Sciences, Schmid College of Science and Technology, Chapman University, Orange, CA 92866, United States.
Joshua G
JG
Jones
D001578:Benzopyrans / Q000737:chemistry*; D006812:Humic Substances; D006861:Hydrogen Peroxide / Q000737:chemistry*; D008956:Models, Chemical; D010777:Photochemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry*
D001578:Benzopyrans; D006812:Humic Substances; D014874:Water Pollutants, Chemical; D006861:Hydrogen Peroxide; C005023:fulvic acid
CDOM; Fulvic; Humic; Hydrogen peroxide; Quinone