Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/hess-2016-377
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
30 Aug 2016
Review status
A revision of this discussion paper was accepted for the journal Hydrology and Earth System Sciences (HESS) and is expected to appear here in due course.
DOM quality in a peatland and forest headwater stream: seasonal and event characteristics
Tanja Broder1,2, Klaus-Holger Knorr2, and Harald Biester1 1IGÖ, Umweltgeochemie, TU Braunschweig, Langer Kamp 19c, 38106 Braunschweig, Germany
2ILÖK, Hydrologie, WWU Münster, Heisenbergstr. 2, 48149 Münster, Germany
Abstract. Peatlands and peaty riparian zones are major sources of DOM, but are poorly understood in terms of export dynamics and controls thereof. The quality of DOM affects function and behavior of DOM in aquatic ecosystems, but DOM quality can also help to track DOM sources and their export dynamics under specific hydrologic preconditions. The objective of this study was to elucidate controls on temporal variability in DOM concentration and quality in discharge from a bog and a forested peaty riparian zone, particularly considering drought and storm flow events. DOM quality was monitored using spectrofluorometric indices for aromaticity (SUVA254), apparent molecular size (SR) and precursor organic material (FI), as well as PARAFAC modeling of excitation emission matrices (EEMs).

Indices for DOM quality exhibited major changes due to different hydrologic conditions, but patterns were also dependent on season. The forested site with mineral, peaty soils generally exhibited higher variability in concentrations and quality compared to the outflow of an ombrotrophic bog. During snowmelt and spring events surface-near protein-like DOM pools were exported. During drought a microbial DOM fraction originating from groundwater and deep peat layers was exported, characterized by high FI, high SR and increasing humic-like fluorophores C1% or C4%. During discharge events this deep sourced DOM pool was diluted by humic-rich surface-near DOM pools, which were more aromatic, also of microbial origin with high FI and SR, and an increase in humic-like fluorophores C2% and C3% at the forested site. The FI suggested export of DOM of strong microbial alteration particularly under discharge events with dry preconditions. This might be due to accelerated microbial activity in the peaty riparian zone of the forested site. Our study demonstrated that DOM export dynamics are not only a passive mixing of different hydrological sources, but assessing DOM quality can greatly improve our understanding of DOM sources and their response under different hydrological preconditions.


Citation: Broder, T., Knorr, K.-H., and Biester, H.: DOM quality in a peatland and forest headwater stream: seasonal and event characteristics, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-377, in review, 2016.
Tanja Broder et al.
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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RC1: 'Review on Broder et al.', Anonymous Referee #1, 07 Oct 2016 Printer-friendly Version 
AC1: 'author's response to referee #1', Tanja Broder, 25 Nov 2016 Printer-friendly Version Supplement 
 
RC2: 'Review', Anonymous Referee #2, 11 Oct 2016 Printer-friendly Version 
AC2: 'author's response to referee #2', Tanja Broder, 25 Nov 2016 Printer-friendly Version Supplement 
Tanja Broder et al.
Tanja Broder et al.

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Short summary
Peatlands and riparian zones are sources of dissolved organic matter (DOM) and the quality of exported DOM to surface waters affects function and behavior of DOM. We present high resolution data of DOM concentration and quality from a headwater catchment, which enabled us to disentangle the role of bog or forested peaty riparian zones in stream DOM dynamics. Our results highlight the importance of high-resolution studies as main changes in DOM quality are triggered by hydrologic (pre)conditions.
Peatlands and riparian zones are sources of dissolved organic matter (DOM) and the quality of...
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