The fate of suspended sediment and particulate organic carbon in transit through the channels of a river catchment

Worrall, Fred; Burt, Tim; Howden, Nicholas J K; Hancock, Gregory R.; Wainwright, John

doi:10.1002/hyp.11413

Cited by 11 publications

(8 citation statements)

References 54 publications

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“…However, the cause of transformation of deep‐peat‐derived fluvial organic carbon is less clear. The variable fates of POC in fluvial systems (Worrall et al, ) will likely be accompanied by large variability over time that is dependent on multiple environmental factors. The continued erosion of peatland carbon stores will therefore not only impact terrestrial carbon but also associated riverine systems as equally complex environments.…”

Section: Resultsmentioning

confidence: 99%

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Controls on fluvial carbon efflux from eroding peatland catchments

Brown

Goulsbra

Evans

2018

Hydrological Processes

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Global peatlands store an unparalleled proportion of total global organic carbon but it is vulnerable to erosion into fluvial systems. Fluvial networks are being recognized as areas of carbon transformation, with eroded particulate organic carbon processed to dissolved organic carbon and CO2. Existing studies indicate biodegradation and photodegradation as key processes controlling the transformation of organic carbon in fluvial systems, with initial concentrations of dissolved organic carbon (DOC) identified as a control on the rate of carbon mineralization. This study manipulates temperature and incident light intensity to investigate carbon mineralization rates in laboratory simulations of peatland sediment transport into fluvial systems. By directly measuring gaseous CO2 emissions from sampled stream water, the relationship of temperature and light intensity with carbon efflux is identified. In simulations where sediment (as particulate organic matter, POM) is absent, temperature is consistently the dominant factor influencing carbon efflux rates. This influence is independent of the initial DOC concentration of the water sample. In simulations where POM was added, representing a peatland river receiving eroded terrestrial sediment, initial DOC concentration predicts 79% of the variation in total gaseous carbon efflux whereas temperature and light intensity predict 12% and 3%, respectively. When sampled stream water's mineralization rates in the presence of added POM are analysed independently, removing DOC as a model variable, the dominant variable affecting CO2 efflux is opposite for each sample. This study presents novel data suggesting peatland erosion introduces further complexity to dynamic stream systems where rates of carbon transformation processes and the influence of specific environmental variables are interdependent. Anthropogenic climate change is identified as a leading risk factor perpetuating peatland erosion; therefore, understanding the fate of terrestrial sediment in rivers and further quantifying the benefits of protecting peatland soils will be of increasing importance to carbon budgeting and ecosystem function studies.

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Section: Resultsmentioning

confidence: 99%

“…However, the cause of transformation of deep-peat-derived fluvial organic carbon is less clear. The variable fates of POC in fluvial systems (Worrall et al, 2018) will likely be accompanied by large variability over time that is dependent on multiple environmental factors.…”

Section: Resultsmentioning

confidence: 99%

Controls on fluvial carbon efflux from eroding peatland catchments

Brown

Goulsbra

Evans

2018

Hydrological Processes

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“…Finally, given the information estimated for each catchment, the velocity profile could be compared with the predicted behaviour of particles based upon the (Hjulström, 1939) curve. The estimated velocity profile at bankfull discharge was compared with the multinomial approximation to the Hjulström curves calculated by Worrall et al (2018) dividing, firstly, deposition from transport and, secondly, transport from erosion. The equations were applied for grain sizes between 2 μm and 2 mm, and then, given the bankfull stream velocity predicted for each reach for each of the study rivers, each reach of the river could be classified as depositing, transporting or eroding for a given particle size.…”

Section: Application Of the Hjulström Curvementioning

confidence: 99%

The problem of underpowered rivers

Worrall

Burt

Hancock

et al. 2020

Earth Surf Processes Landf

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This study has hypothesized that for many rivers the trade‐off between flow accumulation and the decrease in slope along channel length means that stream power increases downstream and, moreover, that given the low slope angles in headwater and low‐order streams, they would have insufficient stream power to erode let alone transport sediment. The study considered the stream power profile, the particle travel distances and the application of the Hjulström curve based on the velocity profile of nine, large UK catchments. The study showed that: Some rivers never showed a maximum in their longitudinal stream power profile, implying that some rivers never develop a deposition zone before they discharge at the tidal limit. Particle travel distances during a bankfull discharge event showed that for some rivers 91% of the upper main channel would not be cleared of sediment. Furthermore, while some rivers could transport a 2 mm particle their entire length in one bankfull event, for another river it would take 89 such events. The Hjulström curve shows that for three of the study rivers the upper 20 km of the river was not capable of eroding a 2 μm particle. The study has shown that for all rivers studied, erosion is focused downstream and deposition upstream. Many UK rivers have a dead zone where, on time scales of the order of centuries, no erosion or transport occurs and erosion only occurs in the lower courses of the channel where discharge rather than slope dominates – we propose these as underpowered rivers. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd

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“…Nevertheless, Worrall et al (2018) estimated overbank storage as 2% in a study of the River Trent, UK, using estimates of the proportion of bankfull discharge to estimate overbank sedimentation. Nevertheless, Worrall et al (2018) estimated overbank storage as 2% in a study of the River Trent, UK, using estimates of the proportion of bankfull discharge to estimate overbank sedimentation.…”

Section: Implications Of Poc Deposition Versus Pedogenesismentioning

confidence: 99%

“…Comparison of the floodplain storage of the fluvial POC flux in this catchment (0.8-4.5%) to other studies is difficult, since most relevant studies involve landscape-scale catchments which do not consist of organic-dominated soils. Nevertheless, Worrall et al (2018) estimated overbank storage as 2% in a study of the River Trent, UK, using estimates of the proportion of bankfull discharge to estimate overbank sedimentation. Gomez et al (2003) estimated that floodplain storage of the Waipaoa river in New Zealand was 4% of the annual POC flux.…”

Section: Implications Of Poc Deposition Versus Pedogenesismentioning

confidence: 99%

Geomorphological controls on fluvial carbon storage in headwater peatlands

Alderson

Evans

Rothwell

et al. 2019

Earth Surf Processes Landf

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Geomorphological controls and catchment sediment characteristics control the formation of floodplains and affect their capacity to sequester carbon. Organic carbon stored in floodplains is typically a product of pedogenic development between periods of mineral sediment deposition. However, in organically‐dominated upland catchments with a high sediment load, eroded particulate organics may also be fluvially deposited with potential for storage and/or oxidation. Understanding the redistribution of terrestrial carbon laterally, beyond the bounds of river channels is important, especially in eroding peatland systems where fluvial particulate organic carbon exports are often assumed to be oxidised. Floodplains have the potential to be both carbon cycling hotspots and areas of sequestration. Understanding of the interaction of carbon cycling and the sediment cascade through floodplain systems is limited. This paper examines the formation of highly organic floodplains downstream of heavily eroded peatlands in the Peak District, UK. Reconstruction of the history of the floodplains suggests that they have formed in response to periods of erosion of organic soils upstream. We present a novel approach to calculating a carbon stock within a floodplain, using XRF and radiograph data recorded during Itrax core scanning of sediment cores. This carbon stock is extrapolated to the catchment scale, to assess the importance of these floodplains in the storage and cycling of organic carbon in this area. The carbon stock estimate for the floodplains across the contributing catchments is between 3482‐13460 tonnes, equating on an annualised basis to 0.8‐4.5% of the modern‐day POC flux. Radiocarbon analyses of bulk organic matter in floodplain sediments revealed that a substantial proportion of organic carbon was associated with re‐deposited peat and has been used as a tool for organic matter source determination. The average age of these samples (3010 years BP) is substantially older than Infrared Stimulated Luminesence dating which demonstrated that the floodplains formed between 430 and 1060 years ago. Our data suggest that floodplains are an integral part of eroding peatland systems, acting as both significant stores of aged and eroded organic carbon and as hotspots of carbon turnover. © 2019 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.

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The fate of suspended sediment and particulate organic carbon in transit through the channels of a river catchment

Cited by 11 publications

References 54 publications

Controls on fluvial carbon efflux from eroding peatland catchments

Controls on fluvial carbon efflux from eroding peatland catchments

The problem of underpowered rivers

Geomorphological controls on fluvial carbon storage in headwater peatlands

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