Lateral carbon mobilization processes along the freshwater continuum remain poorly constrained despite their fundamental role in the C-cycle. We examine temporal versus spatial variations in isotopic signatures of particulate and dissolved organic carbon and dissolved inorganic carbon transported by Swiss rivers to assess carbon sources and cycling within corresponding watersheds. Prior time-series investigations of small Swiss sub-alpine headwater streams revealed large variations in OC isotopic compositions during baseflow conditions and more homogenous isotopic and generally ¹⁴C-enriched (younger) signatures at elevated discharge. Here, we assess whether these characteristics persist further downstream in higher-order Swiss fluvial systems and explore variations within a seasonal perspective. We also compare isotopic characteristics of a suite of 21 Swiss rivers sampled in summer 2021, a year of extraordinary heavy rainfall, with summer 2022, a year of extreme drought, which drain the five different ecoregions of Switzerland that are characterized by contrasting climatic regimes as well as catchment characteristics. Multivariate Regression Analysis reveals that POC, DOC and DIC ¹⁴C values of streams draining alpine terrain are lower than rivers draining lower elevation terrain, and that ¹⁴C signatures of POC under drought conditions are lower than those under high-flow conditions. Overall, we seek to disentangle the role of different hydrological and drainage basin properties on the flux and composition of carbon exported by Swiss rivers. 

Primary Presenter: Timo Rhyner, ETH Zurich (timo.rhyner@erdw.ethz.ch)

Authors:

Timo Rhyner, ETH Zurich/Geological Institute  (timo.rhyner@erdw.ethz.ch)

Lisa Bröder, ETH Zurich/Geological Institute  (lisa.broeder@erdw.ethz.ch)

Margot White, ETH Zurich/Geological Institute  (margot.white@erdw.ethz.ch)

Benedict Mittelbach, ETH Zurich/Geological Institute  (benedict.mittelbach@erdw.ethz.ch)

Hannah Gies, ETH Zurich/Geological Institute  (hannah.gies@erdw.ethz.ch)

Melissa Schwab, NASA/Jet Propulsion Laboratory  (melissa.schwab@erdw.ethz.ch)

Alexander Brunmayr, Imperial College London/Departement of Physics  (alexander.brunmayr19@imperial.ac.uk)

Frank Hagedorn, WSL Swiss Federal Research Institute  (frank.hagedorn@wsl.ch)

Florian Storck, FOEN Federal Office for the Environment  (florian.storck@bafu.admin.ch)

Lucas Passera, FOEN Federal Office for the Environment  (lucas.passera@bafu.admin.ch)

Negar Haghipour, ETH Zurich/Laboratory of Ion Beam Physics  (negar.haghipour@erdw.ethz.ch)

Juerg Zobrist, Emeritus Scientist EAWAG  ()

Timothy Eglinton, ETH Zurich/Geological Institute  (timothy.eglinton@erdw.ethz.ch)