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Travel time and source variation explain the molecular transformation of dissolved organic matter in an Alpine stream network
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  • Hannes Peter,
  • Gabriel Andreas Singer,
  • Amber J. Ulseth,
  • Thorsten Dittmar,
  • Yves T. Prairie,
  • Tom J Battin
Hannes Peter

Corresponding Author:[email protected]

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Gabriel Andreas Singer
Deparment of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB)
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Amber J. Ulseth
École Polytechnique Fédérale de Lausanne
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Thorsten Dittmar
Research Group for Marine Geochemistry, University of Oldenburg, Institute for Chemistry and Biology of the Marine Environment
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Yves T. Prairie
Université du Québec à Montréal
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Tom J Battin
Swiss Federal Institute of Technology (EPFL)
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Streams and rivers are important components of the carbon cycle as they simultaneously transport and transform terrigenous dissolved organic matter (DOM). The time DOM spends in a stream network is an important constraint on the biogeochemical processes that act upon DOM. We used high-resolution Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) to study the spatial distribution of DOM at the molecular level at more than 100 sites within an Alpine stream network during summer and winter baseflow. We developed a model approximating the time DOM spent in the fluvial network. Discharge-weighted travel time (DWTT) explained the compositional changes of DOM, which differed markedly in summer and winter. We attribute the seasonal differences to differences in source material. Hydrological mixing at confluences was an important driver of the spatial dynamics of DOM. From the spatial patterns of individual DOM compounds we inferred the distribution of sources within the catchment, which differed seasonally. Finally, we estimated the apparent mass transfer coefficients of individual DOM compounds at the network level and identified the oxidative state of DOM as an important factor explaining uptake efficiency. This work contributes to our understanding of the spatial processes, temporal constraints and chemical properties of DOM that regulate the transformation and diagenesis of DOM at the fluvial network scale.
Aug 2020Published in Journal of Geophysical Research: Biogeosciences volume 125 issue 8. 10.1029/2019JG005616