The impact of Superoxide (O2-) on trace metal redox cycles and the reactivity with dissolved organic matter
The superoxide (O2-) radical is suspected to be a critically important species involved in the redox cycling of metal ions in natural waters. In sunlit surface waters O2- is a major product of the photooxidation of colored dissolved organic matter (CDOM) and it can also be produced via phytoplankton...
| Main Authors: | , |
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| Format: | Conference Object |
| Language: | unknown |
| Published: |
2011
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| Subjects: | |
| Online Access: | https://oceanrep.geomar.de/id/eprint/12450/ |
| Summary: | The superoxide (O2-) radical is suspected to be a critically important species involved in the redox cycling of metal ions in natural waters. In sunlit surface waters O2- is a major product of the photooxidation of colored dissolved organic matter (CDOM) and it can also be produced via phytoplankton metabolic processes. Inorganic and organic complexes of Cu(II)/Cu(I) and Fe(II)/Fe(III) can react rapidly with O2- leading to a catalytic cycle for superoxide decay but also reactions with dissolved organic matter are suggested as reaction pathway. Our work conducted during the IPY Geotraces cruise ANTXXIV-3 found Cu to be the major sink of O2- in the Southern Ocean despite being strongly organically complexed. This indicates that the Cu organic complexes react directly with O2-. Contrastingly the reaction with Fe was relatively slow throughout the water column. In the eastern tropical Atlantic (unlike the Southern Ocean) we found a significant reactivity of O2- with CDOM. Maximal reaction rates were adjected to the chlorophyll maximum which suggests production or release of unbleached organic material. This work highlights poorly understood processes which impact on the biogeochemical cycling of relevant trace metals and CDOM in the open ocean. |
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