TY - JOUR

T1 - River Organic Carbon Fluxes Modulated by Hydrodynamic Sorting of Particulate Organic Matter

AU - Repasch, Marisa

AU - Scheingross, Joel S.

AU - Hovius, Niels

AU - Vieth-Hillebrand, Andrea

AU - Mueller, Carsten W.

AU - Höschen, Carmen

AU - Szupiany, Ricardo N.

AU - Sachse, Dirk

N1 - 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.

PY - 2022/2/16

Y1 - 2022/2/16

N2 - 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.

AB - 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.

KW - carbon fluxes

KW - compound-specific stable isotopes

KW - hydrodynamic sorting

KW - NanoSIMS

KW - rivers

KW - sediment transport

U2 - 10.1029/2021GL096343

DO - 10.1029/2021GL096343

M3 - Letter

AN - SCOPUS:85125137115

VL - 49

JO - Geophysical Research Letters

JF - Geophysical Research Letters

SN - 0094-8276

IS - 3

M1 - e2021GL096343

ER -