Magnetic Resonance Imaging of coarse sediment

Kleinhans, Maarten G.; Jeukens, Cécile R. L. P. N.; Bakker, Chris J.G.; Frings, Roy M.

doi:10.1016/j.sedgeo.2008.07.002

Cited by 28 publications

(21 citation statements)

References 33 publications

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“…Most recently, this has culminated in successful trials of Magnetic Resonance Imaging (MRI) on sand-gravel sediments; these have yielded full 3-D bed structure data in a non-invasive manner (Kleinhans et al, 2008;Haynes et al, 2009). Whilst this embryonic research technique is not without its challenges, it has permitted the first high resolution data (0.3mm) appropriate to detailed structural analysis in the vertical dimension (e.g.…”

Section: Introductionmentioning

confidence: 99%

A new approach to define surface/sub-surface transition in gravel beds

Haynes¹,

Ockelford

Vignaga³

et al. 2012

Acta Geophys.

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A new approach to define surface/sub-surface transition in gravel beds. The vertical structure of river beds varies temporally and spatially in response to hydraulic regime, sediment mobility, grain size distribution and faunal interaction. Implicit are changes to the active layer depth and bed porosity, both critical in describing processes such as armour layer development, surface-subsurface exchange processes and siltation/sealing. Whilst measurements of the bed surface are increasingly informed by quantitative and spatial measurement techniques (e.g. laser displacement scanning), material opacity has precluded the full 3-D bed structure analysis required to accurately define the surface-subsurface transition. To overcome this problem, this paper provides Magnetic Resonance Imaging data of vertical bed porosity profiles. Uniform and bimodal (σ g = 2.1) sand-gravel beds are considered following restructuring under sub-threshold flow durations of 60 and 960 minutes. MRI data are compared to traditional 2.5-D laser displacement scans and six robust definitions of the surface-subsurface transition are provided; these form the focus of discussion.

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Section: Introductionmentioning

confidence: 99%

A new approach to define surface/sub-surface transition in gravel beds

Haynes¹,

Ockelford

Vignaga³

et al. 2012

Acta Geophys.

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“…A volume of soil can be transferred to the laboratory and subjected to a variety of boundary conditions (de Rooij, 1996). Nondestructive three-dimensional mapping with Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) could be used to construct a digital representation (Lehmann et al, 2006;Kleinhans et al, 2008) for use in a flow model. In this case the experiment and the model are representative of soils with pores in reality.…”

Section: A Continuum Of Fieldwork Experiments and Modellingmentioning

confidence: 99%

HESS Opinions On the use of laboratory experimentation: "Hydrologists, bring out shovels and garden hoses and hit the dirt"

Kleinhans

Bierkens

Perk

2010

Hydrol. Earth Syst. Sci.

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Abstract.From an outsider's perspective, hydrology combines field work with modelling, but mostly ignores the potential for gaining understanding and conceiving new hypotheses from controlled laboratory experiments. Sivapalan (2009) pleaded for a question-and hypothesis-driven hydrology where data analysis and top-down modelling approaches lead to general explanations and understanding of general trends and patterns. We discuss why and how such understanding is gained very effectively from controlled experimentation in comparison to field work and modelling. We argue that many major issues in hydrology are open to experimental investigations. Though experiments may have scale problems, these are of similar gravity as the well-known problems of fieldwork and modelling and have not impeded spectacular progress through experimentation in other geosciences.

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“…Constructed wetlands are an important tool for sustainable development both for their role in wastewater treatment and as support for biodiversity and conservation (Kadlec and Wallace 2009). Horizontal sub-surface flow (HSSF) wetlands are essentially a bed of porous material, usually gravel, in which suitable plants, such as the common reed or iris, are grown and through which contaminated water slowly flows enabling the removal of organic matter and particulates (Vymazal 2010).…”

Section: Introductionmentioning

confidence: 99%

“…They are a highly effective way of removing pollutants and increasing the quality of water before it is released back into a water course. There are numerous differing recommendations for the optimum size of gravel to use in a HSSF constructed wetland (Kadlec and Wallace 2009), however, most use gravel in the size range 3-15 mm for at least the top layer.…”

Section: Introductionmentioning

confidence: 99%

“…The current state of the art for the assessment of clogging in constructed wetlands is in situ permeameter-based hydraulic conductivity (HC) tests (Pedescoll et al 2009). These represent a significant major advance in comparison with initial estimations of clogging which were based on water level surveys (Kadlec and Wallace 2009). However, the in situ tests (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Monitoring accelerated clogging of a model horizontal sub-surface flow constructed wetland using magnetic resonance transverse relaxation times

Bencsik¹,

Shamim²,

Morris³

et al. 2013

Int. J. Environ. Sci. Technol.

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Horizontal sub-surface flow wetlands are essentially a bed of porous material in which suitable plants are grown to facilitate the removal of organic matter and particulates from wastewater. The aim of this study is to assess the reliability and accuracy of magnetic resonance transverse relaxation time for monitoring clogging development in a constructed wetland. In this study, three different horizontal subsurface flow constructed wetland models have been produced using tubes packed with different sizes of glass beads with diameter 3, 8 and 14 mm. Accelerated clogging has been achieved by pumping sludge extracted from a real clogged wetland through the bead pack. A desktop MRI tomography system has been used to monitor the transverse relaxation rate as a function of position along the tube and hydraulic conductivity. To corroborate the clogging with magnetic resonance measurements, the head loss was monitored to determine the hydraulic conductivity. Using a bi-exponential fit to the spin echo train data, the slow relaxation rate contribution shows good correlation with the changing hydraulic conductivity. Both fast and slow contributions map well to the expected clog patterns for a constructed wetland. We have demonstrated that there is a linear correlation between the hydraulic conductivity and both parameters of a bi-exponential fit to R 2 eff , but particularly for the case of the short T 2 component.

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Magnetic Resonance Imaging of coarse sediment

Cited by 28 publications

References 33 publications

A new approach to define surface/sub-surface transition in gravel beds

A new approach to define surface/sub-surface transition in gravel beds

HESS Opinions On the use of laboratory experimentation: "Hydrologists, bring out shovels and garden hoses and hit the dirt"

Monitoring accelerated clogging of a model horizontal sub-surface flow constructed wetland using magnetic resonance transverse relaxation times

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Magnetic Resonance Imaging of coarse sediment

Cited by 28 publications

References 33 publications

A new approach to define surface/sub-surface transition in gravel beds

A new approach to define surface/sub-surface transition in gravel beds

HESS Opinions On the use of laboratory experimentation: &quot;Hydrologists, bring out shovels and garden hoses and hit the dirt&quot;

Monitoring accelerated clogging of a model horizontal sub-surface flow constructed wetland using magnetic resonance transverse relaxation times

Contact Info

Product

Resources

About

HESS Opinions On the use of laboratory experimentation: "Hydrologists, bring out shovels and garden hoses and hit the dirt"