Sedimentary radiocarbon signatures reveal persistent input of soil organic matter into Lake Constance
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Date
2022-09-13Type
- Other Conference Item
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Abstract
Inland waters play a crucial role in the global carbon cycle, as the sequestration of organic carbon (OC) in lake sediments constitutes a sink of atmospheric CO2. Notably, the source of this sequestered OC has important implications for carbon cycling and climate. The burial of recently synthesized terrestrial and aquatic biospheric OC and of aged, soil‐derived OC represents a drawdown of atmospheric CO2. In contrast, erosion, transport, and reburial of rock‐derived OC exert no net effect on atmospheric CO2 levels.
Radiocarbon can be used to differentiate between these different sources of OC and constrain
proportions of recent, pre‐aged, and fossil carbon. Moreover, the 20th‐Century radiocarbon “bomb
spike” offers the possibility to resolve organic matter turnover and transport on decadal timescales. We
combine 14C and stable δ13C isotope signatures of bulk OC from sediment cores retrieved from
perialpine Lake Constance to assess the nature and dynamics of OC accumulation over the last century.Information about OC source isotope signatures was gathered from soil and bedrock profiles in the catchment as well as sediment traps in the lake.
Our results show a muted, but distinct, bomb spike with Δ14C values of bulk OC increasing from ‐250‰ to ‐100‰ in the early 1960s. A linear mixing model reveals that soil‐derived, pre‐aged carbon comprises the largest contributor to the bulk sedimentary OC pool. We attribute the presence of the bomb spike signal to inputs of aquatic biomass, arguing for a rapid incorporation of bomb carbon into the lake DIC pool. Show more
Publication status
publishedBook title
Book of Abstracts 24th Radiocarbon - 10th ¹⁴C & Archaeology ConferencePages / Article No.
Publisher
ETH ZurichEvent
Subject
Radiocarbon; 14C; Lake sediments; BiogeochemistryOrganisational unit
03868 - Eglinton, Timothy I. / Eglinton, Timothy I.
Funding
193770 - Radiocarbon Inventories of Switzerland (RICH): An integrated approach to understand the changing carbon cycle (SNF)
Notes
Conference lecture held on September 13, 2022.More
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