Infiltration into soils, with particular reference to its visualization and measurement by magnetic resonance imaging (MRI)

Amin, M. H. G.; Hall, Laurance D.; Chorley, Richard J.; Richards, Keith

doi:10.1177/030913339802200201

Cited by 19 publications

(6 citation statements)

References 108 publications

(126 reference statements)

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“…A more widely used compatible technique is Nuclear Magnetic Resonance (NMR) analysis, which allows imaging of fluid flow in porous media and also provides information about pore size distributions (e.g. Watson & Chang 1997;Amin et al 1998;Baraka-Lokmane et al 2001). Its use for geological materials is limited by the rather low resolution and by the problems that can be caused by the presence of iron compounds.…”

Section: Future Developmentsmentioning

confidence: 99%

Applications of X-ray computed tomography in the geosciences

et al. 2003

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X-ray computed tomography (CT) is a non-destructive technique with wide applications in various geological disciplines. It reveals the internal structure of objects, determined by variations in density and atomic composition. Large numbers of parallel 2D sections can be obtained, which allows 3D imaging of selected features. Important applications are the study of porosity and fluid flow, applied to investigations in the fields of petroleum geology, rock mechanics and soil science. Expected future developments include the combined use of CT systems with different resolutions, the wider use of related X-ray techniques and the integration of CT data with results of compatible non-destructive techniques.X-ray computed tomography (CT) is a nondestructive technique that allows visualization of the internal structure of objects, determined mainly by variations in density and atomic composition. It requires the acquisition of one-or two-dimensional radiographs for different positions during step-wise rotation around a central axis, whereby either the source and detector or the sample are moved. This is followed by the reconstruction of two-dimensional cross-sections perpendicular to the axis of rotation.CT images record differences in the degree of attenuation of the X-rays, which is materialand energy-dependent. The interactions that are responsible for this attenuation are mainly Compton scattering and photoelectric absorption. The contribution of the photoelectric effect depends on the effective atomic number and is especially important at low energies. At high energies, the Compton effect predominates and attenuation is mainly determined by density.X-ray CT was developed as a medical imaging technique in the early 1970s (Hounsfield 1972(Hounsfield , 1973. The possibility of its use in geology and engineering was soon recognised, resulting in large numbers of publications from the early 1980s onwards. Early applications include studies in the fields of soil science (Petrovic et al. In this introductory paper, we present some general information about the technique and a brief overview of its applications in geology, with references to some recent studies. More detailed information can be found in recent review articles by Duliu (1999) and Ketcham & Carlson (2001). Acquisition of transmission dataThe basic components of X-ray CT scanners are an X-ray source, a detector and a rotation system. Various possible configurations exist, whereby the selected configuration is determined by sample size and the desired resolution, besides availability and access restrictions. Ideally, the X-ray beam should be parallel rather than fanor cone-shaped (with a finite size of the origin), in which case the resolution is only determined by detector quality. High resolution (10 ~tm) can also be attained with microfocus X-ray tubes. Another aspect of acquisition is the energy spectrum of the X-ray source. Unless the X-rays are produced by radioactive decay, they are always polychromatic with a wide range in energy. This compli...

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Section: Future Developmentsmentioning

confidence: 99%

Applications of X-ray computed tomography in the geosciences

et al. 2003

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“…On the other hand, a basic technical challenge in investigations of mass transport in soils is the need for a quantitative, visible and nondestructive monitoring of spatial and temporal water distribution, as a prelude to its quantitative analysis. Magnetic resonance imaging (MRI) is becoming an important tool for studies of patterns and mechanisms of water infiltration into soils (Amin et al, 1998;Posadas et al, 1996). This paper proposes an innovation in the characterization of preferential flow by combining MRI (Posadas et al, 1996;Crestana and Posadas, 1998) with multifractal theory (Chhabra et al, 1989b;Posadas et al, 2001Posadas et al, , 2003 for a three dimensional description of the dynamics of fingers in sandy soils.…”

Section: Introductionmentioning

confidence: 99%

Characterizing water fingering phenomena in soils using magnetic resonance imaging and multifractal theory

Posadas

Quiroz

Tannús

et al. 2009

Nonlin. Processes Geophys.

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Abstract. The study of water movement in soils is of fundamental importance in hydrologic science. It is generally accepted that in most soils, water and solutes flow through unsaturated zones via preferential paths or fingers. This paper combines magnetic resonance imaging (MRI) with both fractal and multifractal theory to characterize preferential flow in three dimensions. A cubic double-layer column filled with fine and coarse textured sand was placed into a 500 gauss MRI system. Water infiltration through the column (0.15×0.15×0.15 m 3 ) was recorded in steady state conditions. Twelve sections with a voxel volume of 0.1×0.1×10 mm 3 each were obtained and characterized using fractal and multifractal theory. The MRI system provided a detailed description of the preferential flow under steady state conditions and was also useful in understanding the dynamics of the formation of the fingers. The f (α) multifractal spectrum was very sensitive to the variation encountered at each horizontally-oriented slice of the column and provided a suitable characterization of the dynamics of the process identifying four spatial domains. In conclusion, MRI and fractal and multifractal analysis were able to characterize and describe the preferential flow process in soils. Used together, the two methods provide a good alternative to study flow transport phenomena in soils and in porous media.

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“…is only used sparingly in environmental science despite its potential to provide important information regarding environmental processes [8]. A number of NMR microimaging studies have focused on water in soils, sediments, or other types of porous media [10][11][12][13][14][15][16][17][18][19], with earlier studies emphasizing the feasibility of the technology for studying soil processes [10,11,15,[20][21][22]. These studies, which monitored 1 H (water), were able to examine the spatial and temporal water distribution and infiltration in a variety of porous media.…”

Section: Introductionmentioning

confidence: 99%

¹H and¹⁹F nuclear magnetic resonance microimaging of water and chemical distribution in soil columns

Simpson

Gross

et al. 2007

Enviro Toxic and Chemistry

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Nuclear magnetic resonance (NMR) microimaging is a noninvasive and nondestructive technique that has great potential for the study of soil processes. Hydrogen-1 NMR microimaging techniques were used to examine the distribution of water in four different soil cores. Fluorine-19 NMR microimaging is also used to study the transport of three model contaminants (hexafluorobenzene, sodium fluoride, and trifluralin) in soil columns. The 1H water distribution studies demonstrate that NMR microimaging can provide unique detail regarding the nature and location of water in soils. Image distortion (magnetic susceptibility) was observed for soil samples low in water (20-28% by weight) and that contained an iron content of 0.73 to 0.99%. Highly resolved images were obtained for the organic-rich soil (Croatan sample) and also facilitated the analysis of bound and unbound soil water through varying spin echo times. The contaminant studies with 19F NMR demonstrated that preferential flow processes can be observed in soil cores in as little as 16 h. Studies with hexafluorobenzene produced the highest quality images whereas the definition decreased over time with both trifluralin and sodium fluoride as the compounds penetrated the soil. Nonetheless, both 1H and 19F NMR microimaging techniques demonstrate great promise for studying soil processes.

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Infiltration into soils, with particular reference to its visualization and measurement by magnetic resonance imaging (MRI)

Cited by 19 publications

References 108 publications

Applications of X-ray computed tomography in the geosciences

Applications of X-ray computed tomography in the geosciences

Characterizing water fingering phenomena in soils using magnetic resonance imaging and multifractal theory

¹H and¹⁹F nuclear magnetic resonance microimaging of water and chemical distribution in soil columns

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Infiltration into soils, with particular reference to its visualization and measurement by magnetic resonance imaging (MRI)

Cited by 19 publications

References 108 publications

Applications of X-ray computed tomography in the geosciences

Applications of X-ray computed tomography in the geosciences

Characterizing water fingering phenomena in soils using magnetic resonance imaging and multifractal theory

1H and19F nuclear magnetic resonance microimaging of water and chemical distribution in soil columns

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¹H and¹⁹F nuclear magnetic resonance microimaging of water and chemical distribution in soil columns