Aquatic Sciences Meeting, Albuquerque 2001
| SS02 Photochemical Reactions In Surface Waters: A Major Issue in the 21st Century? (Environmental Connections) |
| Date: Thursday, February 15, 2001, Time: 2:45:00 PM |
| Location: San Miguel |
| Sulzberger, B, , Swiss Federal Institute for Environmental Science and Technology (EAWAG), CH-8600 Dübendorf, Switzerland, barbara.sulzberger@eawag.ch |
| Emmenegger, L, , Swiss Federal Laboratories for Materials Testing and Research (EMPA), CH-8600 Dübdendorf, Switzerland, lukas.emmenegger@empa.ch |
| Sigg, L, , Swiss Federal Institute for Environmental Science and Technology (EAWAG), CH-8600 Dübendorf, Switzerland, laura.sigg@eawag.ch |
| Kaiser, E, , Swiss Federal Institute for Environmental Science and Technology (EAWAG), CH-8600 Dübendorf, Switzerland, edith.kaiser@eawag.ch |
| EFFECTS OF SOLAR RADIATION AND DISSOLVED ORGANIC MATTER ON THE REDOX CYCLING OF IRON IN SURFACE WATERS |
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| The effects of solar radiation and dissolved organic matter (DOM) on the redox cycling of iron were investigated in two circumneutral Swiss lakes (Greifensee and Melchsee), and in the River Tagliamento (Italy). The following specific questions were addressed with laboratory and field studies: (i) Do the origin and chemical composition of DOM affect the kinetics of light-induced redox cycling of iron? (ii) Does light-induced reduction of Fe(III) proceed via photolysis of Fe(III) complexes or through reduction by superoxide? (iii) Which DOM fraction is most effective in promoting light-induced reduction of Fe(III)? Irradiation of water samples from the two lakes with simulated sunlight revealed a considerably faster kinetics of Fe(III) reduction and of apparent Fe(II) oxidation in Melchsee than in Greifensee, although Fe(II) steady-state concentrations were similar in samples from both lakes. These experimental results, combined with kinetic modeling, suggest that superoxide may be a key parameter for light-induced iron redox cycling in these lakes. Irradiation experiments with water samples from the River Tagliamento suggest that in this river high-molecular weight DOM is most effective in promoting light-induced reduction of Fe(III). |
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