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  • 1
    Language: English
    In: Vadose Zone Journal, 2012, Vol.11(1), p.0
    Description: Advancements in noninvasive imaging methods such as X-ray computed tomography (CT) have led to a recent surge of applications in porous media research with objectives ranging from theoretical aspects of pore-scale fluid and interfacial dynamics to practical applications such as enhanced oil recovery and advanced contaminant remediation. While substantial efforts and resources have been devoted to advance CT technology, microscale analysis, and fluid dynamics simulations, the development of efficient and stable three-dimensional multiphase image segmentation methods applicable to large data sets is lacking. To eliminate the need for wet-dry or dual-energy scans, image alignment, and subtraction analysis, commonly applied in X-ray micro-CT, a segmentation method based on a Bayesian Markov random field (MRF) framework amenable to true three-dimensional multiphase processing was developed and evaluated. Furthermore, several heuristic and deterministic combinatorial optimization schemes required to solve the labeling problem of the MRF image model were implemented and tested for computational efficiency and their impact on segmentation results. Test results for three grayscale data sets consisting of dry glass beads, partially saturated glass beads, and partially saturated crushed tuff obtained with synchrotron X-ray micro-CT demonstrate great potential of the MRF image model for three-dimensional multiphase segmentation. While our results are promising and the developed algorithm is stable and computationally more efficient than other commonly applied porous media segmentation models, further potential improvements exist for fully automated operation. Journal Article.
    Keywords: Engineeringalgorithms ; Computerized Tomography ; Efficiency ; Fluids ; Glass ; Image Processing ; Optimization ; Three-Dimensional Calculations;
    ISSN: Vadose Zone Journal
    E-ISSN: 1539-1663
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  • 2
    Language: English
    In: Soil Science Society of America Journal, 2013, Vol.77(2), pp.403-411
    Description: The influence of clay content in soil-pore structure development and the relative importance of macroporosity in governing convective fluid flow are two key challenges toward better understanding and quantifying soil ecosystem functions....
    Keywords: Life Sciences ; Agricultural Sciences ; GAS ; Models ; Consequences ; Porosity ; Air Permeability ; Parameters ; Transport ; Microtomography ; Quantification ; Agriculture
    ISSN: 0361-5995
    E-ISSN: 1435-0661
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  • 3
    Language: English
    In: Geoderma, January 2015, Vol.237-238, pp.9-20
    Description: Soil macropores largely control fluid and solute transport, making visualization and quantification of macropore characteristics essential for better understanding and predicting soil hydrogeochemical functions. In this study, seventeen large (19 × 20 cm) intact soil cores taken across a loamy field site (Silstrup, Denmark) were scanned at in-situ sampling conditions (~ field capacity) at a relatively coarse resolution (500 μm) by medical X-ray computed tomography (CT). In the image analyses, artifacts related to the presence of rocks were identified and removed before linking CT-derived pore parameters to measured fluid transport parameters. After CT scanning, soil cores were saturated and drained at − 20 hPa soil–water potential, leaving only pores 〉 150 μm air-filled. Air permeability (k ) and air-filled porosity (ε ) were measured to evaluate gas transport behavior in macropore networks under these conditions. Finally, tracer transport experiments at a constant, high flow rate (10 mm h ) were carried out, and the arrival time for 5% of the applied tracer (T ) was used as an index for the magnitude of water transport in macropores. Although X-ray CT scanning only identified 5–25% of the total air-filled pore network at − 20 hPa, CT-derived macroporosity (average for whole column) and macroporosity for the limiting-quarter section of each column were highly correlated to both k and T (R from 0.6 to 0.8). The CT-inferred limiting depth for soil–gas transport was typically located at 90–165 mm depth, and likely a result of soil management history. Results suggest that the functional macropore network for fluid transport was well quantified by rapid, coarse-resolution X-ray CT scanning. Linking rapid X-ray CT scanning with classical fluid transport measurements on large intact columns thus proves highly useful for characterizing soil macropore functions and in perspective may prove to be useful in predicting field-scale variations in gas, water, and chemical transport.
    Keywords: Macropores ; Limiting-Section Macroporosity ; X-Ray Computed Tomography ; Air Permeability ; 5% Tracer Arrival Time ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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  • 4
    Language: English
    In: Geoderma, 15 August 2018, Vol.324, pp.119-130
    Description: Soil liming has demonstrated to be efficient to make acidic soils suitable to agriculture but little research has been done to evaluate its effect on soil structure in the microscale. X-ray microtomography (μCT) is a useful technique to obtain valuable information about the micromorphological characteristics of soil and, thus, can provide important insight into how liming affects such a porous system. In this study, μCT was used to evaluate changes on micromorphological and geometrical properties (porosity, number of pores, pore length, elongation, shape, connectivity and tortuosity) of a soil cultivated under no-tillage system (NTS) caused by the application of lime on the surface. A degraded pasture area representing soil conditions before the NTS implementation was also analyzed. Samples from two soil layers (0–10 cm, A, and 10–20 cm, B) were analyzed with a voxel size of 60 μm. Image visualization, processing and analysis were performed in the Avizo Fire software. Liming improved the soil chemical attributes only at layer A where it also produced positive effects on the soil porous system within a period of thirty months. We highlight the increase in soil porosity and number of pores into which the main soil pore was separated, as evidences of liming effects. At layer A, those pores were found to be more elongated and more connected for the limed site. However, changes in the pattern of the separated pores, with the formation of cylindrical pores in the horizontal orientation for the limed site, were observed at both soil layers, which can be attributed to stimulation of the soil fauna activity due to liming.
    Keywords: Soil Porous System ; 3d Image Analysis ; Microtomography ; Soil Structure ; Soil Quality ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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  • 5
    Language: English
    In: Geoderma, April 2014, Vol.217-218, pp.181-189
    Description: The study characterized soil structure development and evolution in six plots that were amended with varying amounts of animal manure (AM) and NPK fertilizer over a period of 106 years in a long-term fertilization experiment in Bad Lauchstädt, Germany. Two intact soil cores (10-cm diameter and 8-cm tall) and bulk soil samples were extracted from a depth between 5 and 15-cm from each plot. Soil properties including texture, organic carbon, soil–water characteristic, air permeability and diffusivity were measured and analyzed along with X-ray computed tomography (CT) data. Long-term applications of AM and NPK had a major impact on soil organic carbon content which increased from 0.015 kg kg (unfertilized plot) to 0.024 kg kg (well fertilized plot, 30 T ha 2y AM with NPK). Total porosity linearly followed the organic carbon gradient, increasing from 0.36 to 0.43 m m . The water holding capacity of the soil was considerably increased with the increase of AM and NPK applications. Gas diffusivity and air permeability measurements clearly indicated that the level of soil aeration improved with increasing AM and NPK fertilizer amount. The three-dimensional X-ray CT visualizations revealed higher macroporosity and biological (earthworm) activity in the well fertilized areas when compared to plots without or only a small amount of fertilizer applied. A combined evaluation of the soil water characteristic, gas transport and X-ray CT results suggested that pore size distributions widened, and pore connectivity was significantly improved with increasing fertilizer amount. Furthermore, the soils fertilized with both AM and NPK showed a more aggregated structure than soils amended with AM only.
    Keywords: Animal Manure ; Npk Fertilizers ; Soil–Water Characteristic ; Gas Diffusivity ; Air Permeability ; X-Ray Computed Tomography ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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  • 6
    Language: English
    In: Vadose Zone Journal, 01 November 2011, Vol.10(4)
    Description: Engineered capillary barriers typically consist of two layers of granular materials designed so that the contrast in material hydraulic properties and sloping interface retains infiltrating water in the upper layer. We report here on the results of two bench-top capillary barrier experiments, interpretation, and numerical modeling. We measured hydraulic parameters for two coarse materials using standard methods and found that the materials had similar hydraulic properties despite being morphologically different (round vs. angular). The round sand provided a better functioning capillary barrier than the angular sand, but neither experiment could be characterized as a perfectly working capillary barrier. In both cases, more than 93% of the infiltrating water was successfully diverted from the lower layer, however, infiltration into the underlying layer was observed in both systems. Based on this work, we believe that non-continuum processes such as vapor diffusion and film flow contribute to the observed phenomena and are important aspects to consider with respect to capillary barrier design, as well as dry vadose zone processes in general. Using a theoretical film flow equation that incorporates the surface geometry of the porous material we found that infiltration into the coarse underlying sand layer appeared to be dominated by water film flow. The NUFT (Non-isothermal Unsaturated-saturated Flow and Transport) model was used for qualitative comparison simulations. We were able to reproduce the barrier breach observed in the experiments using targeted parameter adjustment, by which pseudo-film flow was successfully simulated.
    Keywords: Materials Science ; Engineering ; Design ; Diffusion ; Film Flow ; Geometry ; Granular Materials ; Hydraulics ; Performance ; Porous Materials ; Sand ; Simulation ; Transport ; Water ; Water Film, Vadose Zone, Capillary Barrier ; Agriculture ; Engineering
    ISSN: 1539-1663
    E-ISSN: 1539-1663
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  • 7
    In: Soil Science Society of America Journal, Nov-Dec, 2002, Vol.66(6), p.1752(8)
    Description: The objective of the presented study was to develop a single probe that can be used to determine soil water retention curves in both laboratory and field conditions, by including a coiled time domain reflectometry (TDR) probe around the porous cup of a standard tensiometer. The combined tensiometer-coiled TDR probe was constructed by wrapping two copper wires (0.8 mm diam. and 35.5 cm long) along a 5-cm long porous cup of a standard tensiometer. The dielectric constant of five different soils (Oso Flaco [coarse-loamy, mixed Typic Cryorthod-fine-loamy, mixed, mesic Ustollic Haplargid], Ottawa sand [F-50-silica sand], Columbia [Coarse-loamy, mixed, superactive, nonacid, thermic Oxyaquic Xerofluvents], Lincoln sandy loam (sandy, mixed, thermic Typic Ustifluvents), and a washed sand--SRI30) was measured with the combined tensiometer-coiled TDR probe (coil) as a function of the soil water content ([theta]) and soil water matric potential (h). The measured dielectric constant ([[epsilon].sub.coil) as a function of water content was empirically fitted with a third-order polynomial equation, allowing estimation of 0(h)-curves from the combined tensiometer-coiled TDR probe measurements, with [R.sup.2] values larger than 0.98. In addition, the mixing model approach, adapted for the tensiometer-coiled TDR probe, was successful in explaining the functional form of the coiled TDR data with about 30% of the coiled-TDR probe measurement explained by the bulk soil dielectric constant. This new TDR development provides in situ soil water retention data from simultaneous soil water matric potential and water content measurements within approximately the same small soil volume around the combined probe, but requires soil specific calibration because of slight desaturation of the porous cup of the tensiometer.
    Keywords: Soil Moisture -- Measurement ; Reflectometers -- Research ; Tensiometers -- Research
    ISSN: 0361-5995
    E-ISSN: 14350661
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  • 8
    Language: English
    In: Geoderma, 15 March 2019, Vol.338, pp.585-596
    Description: The hierarchical organization of aggregates in soil is responsible for the presence of inter and intra-aggregate pores. This research aimed to investigate effects of soil surface liming, considering lime rates of 0, 10 and 15 t ha , on the intra-aggregate porous system of soil aggregates with equivalent diameters of 2–4 and 1–2 mm, from 0 to 10 (A) and 10 to 20 cm (B) soil layers. These aggregates were selected by the wet sieving method carried out for determination of the mean weight diameter. Synchrotron-based computed microtomography (μCT) of aggregates was analyzed in terms of porosity, connectivity, tortuosity, and fractal dimension. Additionally, X-ray fluorescence was used to evaluate the elemental composition of the soil aggregates. All liming effects were concentrated at layer A, where calcium percentage was elevated in aggregates from 1–2 mm class as compared to those from 2–4 mm class. Accordingly, the physical parameters studied were generally more affected in the case of smaller aggregates (1–2 mm). Liming decreased total porosity, increased tortuosity of pores, and decreased fractal dimension for 1–2 mm aggregates, which was in line with the fact that larger pores were replaced by smaller ones in 1–2 mm aggregates, as found both quantitative and qualitative analyses. On the other hand, liming did not affect pore connectivity under any of the circumstances.
    Keywords: Soil Aggregate ; Porosity ; Tortuosity ; Connectivity ; Fractal Dimension ; Liming ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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