River Organic Carbon Fluxes Modulated by Hydrodynamic Sorting of Particulate Organic Matter
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Rivers regulate the global carbon cycle by transferring particulate organic carbon (POC) from terrestrial landscapes to marine sedimentary basins, but the processes controlling the amount and composition of fluvially exported POC are poorly understood. We propose that hydrodynamic sorting processes modify POC fluxes during fluvial transit. We test this hypothesis by studying POC transported along a ∼1,200 km reach of the Rio Bermejo, Argentina. Nanoscale secondary ion mass spectrometry revealed that POC was either fine, mineral-associated organic matter, or coarse discrete organic particles. Mineral-associated POC is more resistant to oxidation and has a lower particle settling velocity than discrete POC. Consequently, hydraulic sorting and downstream fining amplify the proportion of fine, mineral-associated POC from ∼55% to ∼78% over 1,220 km of downstream transit. This suggests that mineral-associated POC has a greater probability of export and preservation in marine basins than plant detritus, which may be oxidized to CO2 during transit.
Original language | English |
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Article number | e2021GL096343 |
Journal | Geophysical Research Letters |
Volume | 49 |
Issue number | 3 |
Number of pages | 11 |
ISSN | 0094-8276 |
DOIs | |
Publication status | Published - 16 Feb 2022 |
Bibliographical note
Funding Information:
The authors thank Manfred Strecker for support through StRATEGy (Deutsche Forschungsgemeinschaft grant STR 373/34‐1), Doreen Noack and Oliver Rach for assistance with biomarker isotope measurements, Gertraud Harrington and Johann Lugmeier for NanoSIMS analyses, Sathish Mayanna for SEM imaging, and Jens Turowski for discussion. Sample collection was supported by Oscar Orfeo and Roberto Lopez. The supplementary material contains additional text, figures, and tables.
Publisher Copyright:
© 2022. The Authors.
- carbon fluxes, compound-specific stable isotopes, hydrodynamic sorting, NanoSIMS, rivers, sediment transport
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