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Titel |
Redox properties of dissolved organic matter along redox gradients in two peatland-dominated forested catchments |
VerfasserIn |
Markus Schmitt, Michael Sander, Christian Blodau, Stefan Peiffer, Klaus-Holger Knorr |
Konferenz |
EGU General Assembly 2015
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 17 (2015) |
Datensatznummer |
250105905
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Publikation (Nr.) |
EGU/EGU2015-5492.pdf |
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Zusammenfassung |
Dissolved organic matter (DOM) contributes significantly to the carbon cycle and influence
the mobility of metals and contaminants. Water logged, riparian wetlands have been
identified as an important source of DOM in catchments. As DOM export from wetlands
often involves transitions in redox conditions, for a more mechanistic understanding of
sources, mobilization processes and fate of DOM under different redox conditions additional
analytical approaches are needed.
In this study we combined established methods for DOM characterization, such as
fluorescence spectroscopy and δ13CDOC, with mediated electrochemical reduction and
oxidation of DOM for the determination the electron accepting and donating capacity
(EAC/EDC). With this approach, we intended to test if the redox state of DOM can be used
to identify and characterize its sources in catchments. To this end, we collected
samples in two catchments - one dominated by fens and forest, the other by an
ombrotrophic bog - from different hydrological compartments and from different source
materials.
EAC strongly decreased from oxic groundwater (6.4 ± 2.1 mmole- gC -1) to anoxic
peat pore water (0.6 ± 0.5 mmole- gC -1). Contrarily, for EDC, there was no clear pattern to
separate water compartments with different redox states. EDC seemed thus to depend mainly
on the DOM source materials. Results of fluorescence spectroscopy and δ13CDOCconfirmed
that changes in EDC were presumably due to changes in DOC quality rather than
redox state. Moreover, comparing peat pore water and DOM in an adjacent erosion
rill, EDC increased from 0.7 mmole- gC -1 in the anoxic pore water to 1.7 ± 0.2
mmole- gC -1 along the flow path in the oxic stream. This further suggested a
different mobility of different DOM fractions, with higher EDC in more mobile
DOM.
This study indicates that combining electrochemical and spectroscopic methods for
characterization of DOM quality and redox state can improve our understanding of source
and fate of DOM in peatland-dominated forested catchments. |
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