EGU2020-7936
https://doi.org/10.5194/egusphere-egu2020-7936
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

The molecular composition of dissolved organic matter (DOM) and its effects on the greenhouse gas production in pristine subarctic rivers

Taija Saarela1, Helena Jäntti1, Mizue Ohashi3, Jun’ichiro Ide4, Frank Berninger2, Anne Ojala5, and Jukka Pumpanen1
Taija Saarela et al.
  • 1Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, Finland (taija.saarela@uef.fi)
  • 2Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
  • 3School of Human Science and Environment, University of Hyogo, Hyogo, Japan
  • 4Institute of Decision Science for a Sustainable Society, Kyushu University, Fukuoka, Japan
  • 5Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland

Controls on the degradation of dissolved organic matter (DOM) in freshwaters play a major role in the global carbon cycle. Under the changing climate, the aquatic systems are exposed to increasing terrestrial OM load due to changes in precipitation and air temperature. However, little is known about how the source and composition of this DOM influence its microbial processing in receiving waters.

In this study, we aimed to determine the composition of riverine DOM at a molecular level to gain a more comprehensive understanding on how the quality and quantity of DOM reflect its microbial degradability. Our objectives were to determine how the DOM decay patterns differ between brown-water and clearwater river and how these further regulate the potential greenhouse gas production (carbon dioxide, CO2 and methane, CH4) in these waters.

We collected water samples during two sampling occasions (June and October 2018) from two pristine subarctic rivers in Finnish Lapland and conducted 21-day incubation studies to follow the changes in the concentration and molecular composition of DOM, as well as the changes in the CO2 and CH4 concentrations. The molecular characterization of DOM was carried out using electrospray ionization (ESI) coupled to high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS).

Both rivers acted as a source of CO2 and CH4. Our preliminary results show that river water surrounded by peatlands contained a higher number of compounds such as condensed aromatic structures and lignin-like molecules, which led to slower decomposition rates compared to DOM in clearwater river. Overall, the decomposition of DOM was higher during spring flow than during fall due to recently released fresh DOM in the water.

How to cite: Saarela, T., Jäntti, H., Ohashi, M., Ide, J., Berninger, F., Ojala, A., and Pumpanen, J.: The molecular composition of dissolved organic matter (DOM) and its effects on the greenhouse gas production in pristine subarctic rivers, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7936, https://doi.org/10.5194/egusphere-egu2020-7936, 2020

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