Fluvial Organic Carbon Composition Regulated by Seasonal Variability in Lowland River Migration and Water Discharge

Golombek, Nina; Scheingross, Joel S.; Repasch, Marisa; Hovius, Niels; Menges, Johanna; Sachse, Dirk; Lupker, Maarten; Eglinton, T. I.; Haghipour, Negar; Poulson, Simon R.; Gröcke, Darren R.; Latosinski, F.; Szupiany, R. N.

doi:10.1029/2021gl093416

Cited by 12 publications

(9 citation statements)

References 46 publications

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“…Flood conditions may also increase sediment transport capacity and accelerate bank erosion, increasing fluxes of discrete POC. During low-flow conditions, coarse discrete POC is more likely to be deposited and oxidized on braid and point bars due to reduced transport capacity, resulting in predominant export of mineral-associated organic matter from the headwaters (e.g., Golombek et al, 2021). Furthermore, in the Rio Bermejo we observed water-logged plant debris traveling in an undercurrent near the river bed, similar to observations in the Madre de Dios River (Feng et al, 2016).…”

Section: Hydrodynamic Sorting Effects On Fluvial Poc Fluxessupporting

confidence: 76%

“…We found that total Q POC , primarily Q POC, f , increased significantly between downstream km 135 and 420, coincident with an increase in lateral channel migration rate. These results highlight river bank erosion as a key mechanism for delivering mineral‐associated POC to downstream sedimentary basins (Galy et al., 2015; Golombek et al., 2021; Torres et al., 2017), where it can be buried and preserved, contributing to long‐term CO 2 drawdown (Barber et al., 2017; Keil, Tsamakis, et al., 1994; Mead & Goñi, 2008).…”

Section: Hydrodynamic Sorting Effects On Fluvial Poc Fluxesmentioning

confidence: 91%

“…Flood conditions may also increase sediment transport capacity and accelerate bank erosion, increasing fluxes of discrete POC. During low‐flow conditions, coarse discrete POC is more likely to be deposited and oxidized on braid and point bars due to reduced transport capacity, resulting in predominant export of mineral‐associated organic matter from the headwaters (e.g., Golombek et al., 2021).…”

Section: Hydrodynamic Sorting Effects On Fluvial Poc Fluxesmentioning

confidence: 99%

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

Repasch

Scheingross

Hovius

et al. 2022

Geophysical Research Letters

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Cycling of organic carbon (OC) between the lithosphere, biosphere, and atmosphere regulates Earth's climate. Rivers modulate this cycle by redistributing OC from vegetated uplands to sedimentary basins. If fluvially transported OC is preserved during source-to-sink transit, its long-term burial sequesters atmospheric CO 2 over geologic timescales (Berner, 1990;Burdige, 2005;France-Lanord & Derry, 1997). To estimate OC burial fluxes and assess the influence of fluvial transport on the geologic carbon cycle, we need mechanistic explanations of the complex links between the geomorphic and biogeochemical processes driving the sourcing, transport, oxidation, and burial of OC in river systems.Fluvial particulate organic carbon (POC) comprises a mixture of petrogenic POC from organic-rich bedrock (e.g., shale) and biospheric POC from plants and soils (Galy et al., 2015;Rosenheim & Galy, 2012). While petrogenic POC decomposes slowly and can be preserved and recycled through the lithosphere over million-year cycles (Galy, et al., 2008;Scheingross et al., 2019;Sparkes et al., 2020), biospheric POC is physically and chemically unstable at Earth's surface and can be oxidized to CO 2 if not rapidly buried. Biospheric POC can bind

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Section: Hydrodynamic Sorting Effects On Fluvial Poc Fluxessupporting

confidence: 76%

Section: Hydrodynamic Sorting Effects On Fluvial Poc Fluxesmentioning

confidence: 91%

Section: Hydrodynamic Sorting Effects On Fluvial Poc Fluxesmentioning

confidence: 99%

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

Repasch

Scheingross

Hovius

et al. 2022

Geophysical Research Letters

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“…To conclude, multiple flooding events can comprise different proportions of sediment sources and transport processes. This temporal variability applies not only to the inter‐seasonal variation as previously observed (Golombek et al., 2021; Jian et al., 2020) but also to the variations within a single season. The temporal variation observed in this case study poses constraints on the interpretation of compositional differences in terms of sediment provenance, and should be considered in studies of modern drainage basins as well as ancient sediment routing systems.…”

Section: Discussionsupporting

confidence: 61%

Intra‐Seasonal Variability in Sediment Provenance and Transport Processes in the Brahmaputra Basin

et al. 2023

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Sediment composition in modern fluvial settings is commonly assessed regarding spatial but rarely temporal variability, potentially leading to a bias of unknown extent. Here, we present the grain‐size distribution, bulk chemical and mineralogical composition of a time‐series set of 36 suspended sediment samples from the Brahmaputra river, as well as clay and heavy mineral analysis of selected samples. Sampling covers the June–November 2021 period, which included two major flooding events. We show that the two flooding events are characterized by contrasting grain size, with the first event characterized by a grain‐size minimum and the second by a grain‐size maximum. Although grain sizes of the first flood and the period after the second are similar, their compositions differ significantly, highlighted by a factor‐two decrease of biotite largely compensated by an increase in quartz. By contrast, the content of garnet, clinopyroxene, sillimanite, and rutile increased compared to epidote and amphibole during the second flood event. By relating the results to spatio‐temporal rainfall and discharge patterns and basin morphology, we conclude that the first flooding primarily mobilized hydraulically pre‐sorted sediments from the exposed sandbars of the floodplains, while those sandbars are already submerged during the second flooding in a single‐channel system, resulting in higher sediment contributions from highland tributaries draining igneous and high‐grade metamorphic rocks. Such temporal variations pose constraints on the interpretation of compositional differences between individual samples regarding sediment provenance and dispersal and should be considered in studies of modern drainage basins as well as ancient sediment routing systems.

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“…For rivers in the loess area more than 80% of the total suspended sediment can be ascribed to bank erosion and collapse (Simon et al., 2000). In addition, the transit of bank‐derived sediment from a given catchment to the ocean contributes to the global carbon cycle (Galy et al., 2015; Golombek et al., 2021; Repasch et al., 2022). For instance, lateral erosion of rivers cutting through floodplains releases additional organic carbon fluxes to downstream depositional sinks (e.g., tidal flats and deltas).…”

Section: Feedbacks Between Bank Retreat and Morphodynamicsmentioning

confidence: 99%

A Review on Bank Retreat: Mechanisms, Observations, and Modeling

Zhao

Coco

Gong

et al. 2022

Reviews of Geophysics

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Bank retreat plays a fundamental role in fluvial and estuarine dynamics. It affects the cross‐sectional evolution of channels, provides a source of sediment, and modulates the diversity of habitats. Understanding and predicting the geomorphological response of fluvial/tidal channels to external driving forces underpins the robust management of water courses and the protection of wetlands. Here, we review bank retreat with respect to mechanisms, observations, and modeling, covering both rivers and (previously neglected) tidal channels. Our review encompasses both experimental and in situ observations of failure mechanisms and bank retreat rates, modeling approaches and numerical methods to simulate bank erosion. We identify that external forces, despite their distinct characteristics, may have similar effects on bank stability in both river and tidal channels, leading to the same failure mode. We review existing data and empirical functions for bank retreat rate across a range of spatial and temporal scales, and highlight the necessity to account for both hydraulic and geotechnical controls. Based on time scale considerations, we propose a new hierarchy of modeling styles that accounts for bank retreat, leading to clear recommendations for enhancing existing modeling approaches. Finally, we discuss systematically the feedbacks between bank retreat and morphodynamics, and suggest that to move this agenda forward will require a better understanding of multifactor‐driven bank retreat across a range of temporal scales, with particular attention to the differences (and similarities) between riverine and estuarine environments, and the role of feedbacks exerted by the collapsed bank soil.

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Fluvial Organic Carbon Composition Regulated by Seasonal Variability in Lowland River Migration and Water Discharge

Cited by 12 publications

References 46 publications

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

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

Intra‐Seasonal Variability in Sediment Provenance and Transport Processes in the Brahmaputra Basin

A Review on Bank Retreat: Mechanisms, Observations, and Modeling

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