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

Abstract. Studies engaging in tracking headwater carbon signatures downstream remain sparse, despite their importance for constraining transfer and transformation pathways of organic (OC) developing regional-scale perspectives on mechanisms influencing the balance between remineralization export. Based a 40-month time series, we investigate dependence hydrology seasonality discharge sediment OC small (350 km2) Swiss subalpine watershed (Sihl River basin). We analyze concentrations isotopic compositions (δ13C, F14C) particulate use dual-isotope mixing machine learning frameworks to characterize estimate source contributions, transport pathways, export fluxes. The majority transferred is sourced from plant biomass soil material. relative amount bedrock-derived (petrogenic) OC, abundant streams, progressively decreases response lack material efficient overprinting with biospheric illustrating rapid matter alteration over short distances. Large variations observed during baseflow conditions converge form homogenous mixture enriched characterized by higher POC-F14C values following precipitation-driven events. Particulate data model results suggest that storms facilitate surface runoff inundation riparian zones, resulting entrainment loose plant-derived debris surficial Although particle Sihl basin mainly driven hydrology, subtle changes bedrock erosivity, slope angle, floodplain extent likely have profound effects POC composition, age, yields.