X-ray microtomography: A porosity-based thresholding method to improve soil pore network characterization?

Beckers, Éléonore; Plougonven, Erwan; Roisin, Christian; Hapca, Simona M.; Léonard, Angélique; Degré, A.

doi:10.1016/j.geoderma.2014.01.004

Cited by 37 publications

(26 citation statements)

References 36 publications

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“…As was also done by Hellner et al (), we applied this threshold value to all gray‐scale‐calibrated images to obtain binary images depicting the X‐ray resolvable pores. Beckers et al () found that a similar global segmentation method performed as well as local approaches that are more demanding in terms of time and computational resources. Figures a–c depict three example images of samples showing contrasting pore space structure.…”

Section: Methodsmentioning

confidence: 99%

Estimating the Permeability of Naturally Structured Soil From Percolation Theory and Pore Space Characteristics Imaged by X‐Ray

Koestel

Dathe

Skaggs

et al. 2018

Water Resources Research

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The saturated hydraulic conductivity of soil, Ks, is a critical parameter in hydrological models that remains notoriously difficult to predict. In this study, we test the capability of a model based on percolation theory and critical path analysis to estimate Ks measured on 95 undisturbed soil cores collected from contrasting soil types. One parameter (the pore geometry factor) was derived by model fitting, while the remaining two parameters (the critical pore diameter, dc, and the effective porosity) were derived from X‐ray computed tomography measurements. The model gave a highly significant fit to the Ks measurements (p < 0.0001) although only ~47% of the variation was explained and the fitted pore geometry factor was approximately 1 to 2 orders of magnitude larger than various theoretical values obtained for idealized porous media and pore network models. Apart from assumptions in the model that might not hold in reality, this could also be attributed to experimental error induced by, for example, air entrapment and changes in the soil pore structure occurring during sample presaturation and the measurement of Ks. Variation in the critical pore diameter, dc, was the dominant source of variation in Ks, which suggests that dc is a suitable length scale for predicting soil permeability. Thus, from the point of view of pedotransfer functions, it could be worthwhile to direct future research toward exploring the correlations of dc with basic soil properties and site attributes.

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Section: Methodsmentioning

confidence: 99%

Estimating the Permeability of Naturally Structured Soil From Percolation Theory and Pore Space Characteristics Imaged by X‐Ray

Koestel

Dathe

Skaggs

et al. 2018

Water Resources Research

View full text Add to dashboard Cite

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“…Therefore, the PSF theory can be promoted taking the solid surface suction, water potential energy, and the soil pore compaction into account in the next work. Moreover, technologies involving the original SEM39, X-ray4647, and the nuclear magnetic resonance4849 methodologies can be utilized on the soil fractal dimension using a microscopic view, which may give a solution to further determine the parameter D a and D d in future studies.…”

Section: Discussionmentioning

confidence: 99%

A user-friendly modified pore-solid fractal model

Ding

Zhao

Feng

et al. 2016

Sci Rep

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The primary objective of this study was to evaluate a range of calculation points on water retention curves (WRC) instead of the singularity point at air-entry suction in the pore-solid fractal (PSF) model, which additionally considered the hysteresis effect based on the PSF theory. The modified pore-solid fractal (M-PSF) model was tested using 26 soil samples from Yangling on the Loess Plateau in China and 54 soil samples from the Unsaturated Soil Hydraulic Database. The derivation results showed that the M-PSF model is user-friendly and flexible for a wide range of calculation point options. This model theoretically describes the primary differences between the soil moisture desorption and the adsorption processes by the fractal dimensions. The M-PSF model demonstrated good performance particularly at the calculation points corresponding to the suctions from 100 cm to 1000 cm. Furthermore, the M-PSF model, used the fractal dimension of the particle size distribution, exhibited an accepted performance of WRC predictions for different textured soils when the suction values were ≥100 cm. To fully understand the function of hysteresis in the PSF theory, the role of allowable and accessible pores must be examined.

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“…These objective algorithms have been used in a number of investigations (e.g., Beckers et al, 2014a,b; Houston et al, 2017), and new algorithms are appearing that do not require any parameter tuning (e.g., West et al, 2018), but so far they have not stopped the development of operator-dependent approaches (Kulkarni et al, 2012; Hashemi et al, 2014; Ojeda-Magana et al, 2014; Martin-Sotoca et al, 2017). Therefore, further progress is needed in this area, especially in order to segment images containing multiple distinct populations of voxels.…”

Section: Progress On the Physical Frontmentioning

confidence: 99%

Emergent Properties of Microbial Activity in Heterogeneous Soil Microenvironments: Different Research Approaches Are Slowly Converging, Yet Major Challenges Remain

et al. 2018

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Over the last 60 years, soil microbiologists have accumulated a wealth of experimental data showing that the bulk, macroscopic parameters (e.g., granulometry, pH, soil organic matter, and biomass contents) commonly used to characterize soils provide insufficient information to describe quantitatively the activity of soil microorganisms and some of its outcomes, like the emission of greenhouse gasses. Clearly, new, more appropriate macroscopic parameters are needed, which reflect better the spatial heterogeneity of soils at the microscale (i.e., the pore scale) that is commensurate with the habitat of many microorganisms. For a long time, spectroscopic and microscopic tools were lacking to quantify processes at that scale, but major technological advances over the last 15 years have made suitable equipment available to researchers. In this context, the objective of the present article is to review progress achieved to date in the significant research program that has ensued. This program can be rationalized as a sequence of steps, namely the quantification and modeling of the physical-, (bio)chemical-, and microbiological properties of soils, the integration of these different perspectives into a unified theory, its upscaling to the macroscopic scale, and, eventually, the development of new approaches to measure macroscopic soil characteristics. At this stage, significant progress has been achieved on the physical front, and to a lesser extent on the (bio)chemical one as well, both in terms of experiments and modeling. With regard to the microbial aspects, although a lot of work has been devoted to the modeling of bacterial and fungal activity in soils at the pore scale, the appropriateness of model assumptions cannot be readily assessed because of the scarcity of relevant experimental data. For significant progress to be made, it is crucial to make sure that research on the microbial components of soil systems does not keep lagging behind the work on the physical and (bio)chemical characteristics. Concerning the subsequent steps in the program, very little integration of the various disciplinary perspectives has occurred so far, and, as a result, researchers have not yet been able to tackle the scaling up to the macroscopic level. Many challenges, some of them daunting, remain on the path ahead. Fortunately, a number of these challenges may be resolved by brand new measuring equipment that will become commercially available in the very near future.

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X-ray microtomography: A porosity-based thresholding method to improve soil pore network characterization?

Cited by 37 publications

References 36 publications

Estimating the Permeability of Naturally Structured Soil From Percolation Theory and Pore Space Characteristics Imaged by X‐Ray

Estimating the Permeability of Naturally Structured Soil From Percolation Theory and Pore Space Characteristics Imaged by X‐Ray

A user-friendly modified pore-solid fractal model

Emergent Properties of Microbial Activity in Heterogeneous Soil Microenvironments: Different Research Approaches Are Slowly Converging, Yet Major Challenges Remain

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