01 Aug 2022
01 Aug 2022
Status: this preprint is open for discussion.

Environmental and hydrologic controls on sediment and organic carbon export from a subalpine catchment: insights from a time-series

Melissa Sophia Schwab1,a, Hannah Gies1, Chantal Valérie Freymond1,b, Maarten Lupker1,c, Negar Haghipour1,2, and Timothy Ian Eglinton1 Melissa Sophia Schwab et al.
  • 1Department of Earth Sciences, ETH Zurich, Zurich, 8092, Switzerland
  • 2Laboratory of Ion Beam Physics, ETH Zurich, Zurich, 8093, Switzerland
  • anow at: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, 91109, USA
  • bnow at: Gruner, Basel, 4020, Switzerland
  • cnow independent, Bern, 3014, Switzerland

Abstract. Studies engaging in tracking headwater carbon signatures downstream remain sparse, despite their importance for constraining transfer and transformation pathways of organic carbon (OC) and developing regional-scale perspectives on mechanisms influencing the balance between remineralization and carbon export. Based on a 40-month time series, we investigate the dependence of hydrology and seasonality on the discharge of sediment and OC in a small Swiss subalpine watershed (Sihl River basin). We analyze concentrations and isotopic compositions (δ13C, F14C) of particulate OC and use dual-isotope mixing and machine learning frameworks to characterize and estimate source contributions, transport pathways, and export fluxes. The majority of transferred OC is sourced from plant biomass and soil material. Relative proportions of soil-derived particulate OC peak during the summer months, coinciding with maximum soil erosion rates. Bedrock-derived (petrogenic) OC abundant in headwater streams progressively decreases downstream in response to a lack of source material and efficient overprinting with biospheric organic matter, illustrating rapid OC transformation over short distances. Large variations in isotopic compositions observed during baseflow conditions converge and form a homogenous mixture enriched in OC and characterized by higher POC- F14C values following precipitation-driven events. We propose that storms facilitate surface runoff and shallow landsliding, resulting in the entrainment of fresh litter and surficial soil layers. Model results further indicate diverging mobilization pathways. Discharge and water stage describe the export of suspended sediment, while the prediction of POC fluxes is mostly supported by water stage and 1-day antecedent precipitation. Although particle transport in the Sihl River basin is mainly driven by hydrology, subtle changes in bedrock erosivity, slope angle, and floodplain extent likely have profound effects on the POC composition, age, and export yields.

Melissa Sophia Schwab et al.

Status: open (until 12 Sep 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Melissa Sophia Schwab et al.

Melissa Sophia Schwab et al.


Total article views: 90 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
65 21 4 90 8 2 2
  • HTML: 65
  • PDF: 21
  • XML: 4
  • Total: 90
  • Supplement: 8
  • BibTeX: 2
  • EndNote: 2
Views and downloads (calculated since 01 Aug 2022)
Cumulative views and downloads (calculated since 01 Aug 2022)

Viewed (geographical distribution)

Total article views: 80 (including HTML, PDF, and XML) Thereof 80 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
Latest update: 08 Aug 2022
Short summary
The majority of river studies focuses on headwater or floodplain systems, while often neglecting intermediate river segments. Our study on the subalpine Sihl River bridges the gap between streams and lowlands and demonstrates that moderately steep river segments are areas of significant instream transformation, modulating the export of organic carbon over short distances.