C02_03

Radiocarbon Inventories of Switzerland: Spatial Radiocarbon Signatures of Carbon exported by Swiss Rivers

Rhyner T¹,  Haghipour N¹, Bröder L¹, Eglinton T¹

¹ETH, Zurich, Switzerland

In the Anthropocene, there is the need to investigate changes in the nature of carbon within the biosphere, hydrosphere, atmosphere, geosphere and the connection between them. The RICH-project (Radiocarbon Inventories of Switzerland), is a world premiere in constructing a first national-scale census of carbon across aquatic, terrestrial, and atmospheric reservoirs. Within the global carbon cycle, inland waters play a crucial role, where rivers act as principal connectors between different carbon reservoirs. However, there is still limited understanding of the drivers that control carbon mobilization and mineralization in rivers. This project will establish radiocarbon inventories of dissolved and particulate carbon phases across major river systems of Switzerland. In many cases, the inputs of C to a reservoir can derive from multiple sources, where radiocarbon has been used in combination with ¹³C to disentangle a C mixture into its source components of modern, pre-aged, or fossil carbon. This can be used to estimate the relative contributions of individual sources with different ¹⁴C-signatures to a given system. Combining emergent ecosystem properties across the five ecoregions of Switzerland, there will be the notion of a radiocarbon compilation to develop an integrated perspective on carbon cycling on a national scale. A field sampling campaign in 2021 revealed spatial variability in radiocarbon content, where riverine Δ¹⁴C ranged from -477 ‰ to 58 ‰. These data form the foundation for future in-depth investigations using ¹⁴C measurements on compound-specific biomarkers to constrain the temporal dynamics and transport pathways of biospheric carbon.