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Particle-size distribution is a critical part of soil description, which is commonly measured using pipette and hydrometer methods. However, a recently developed technique, called the integral suspension pressure method, allows for the measurement of continuous particle-size distribution based on Stokes' law. The objective of this study was to evaluate the applicability of the integral suspension pressure method for measuring particle-size distribution, as an alternative to the standard hydrometer procedure. The integral suspension pressure method was tested by using a soil dataset with a wide range of organic matter contents (0.22-12.0%). Forty-nine samples were analysed with a hydrometer after organic matter removal and the results were compared with those obtained using the integral suspension pressure method. Through comparing the integral suspension pressure and hydrometer measurements, root mean square error values of 8.9, 8.1, and 11.9% were observed for sand, silt, and clay, respectively. The clay fraction was underestimated throughout the entire range of measurements. Conversely, the silt content was overestimated over the whole range of measurements, especially in samples with more than 36% silt. When compared to the hydrometer method, integral suspension pressure integral suspension pressure exhibited a tendency to misclassify the soil texture of clay loam samples but was accurate for sandy loams. [ABSTRACT FROM AUTHOR]

The capillary effect in polydisperse porous systems of soils and sediments is discussed. This effect is quantified using a new fundamental model of capillary rise depending on the parameters of dispersion of soil particles, soil bulk density, density of soil solid phase, wettability, and the amount of tightly bound water. In contrast to a well-known Jurin's law, the model takes into account the particle-size distributions and the change in pore size associated with soil density. The model adequately predicts the capillary rise in both artificial monodisperse porous systems and real soils with the particle size ranging from 0.006 to 1 mm. The effects of natural and synthetic hydrophobizers on the kinetics and maximum height of capillary rise are examined. The laboratory and field data on the efficiency of imperfect (with hydraulic connection) and perfect (with its rupture) capillary barriers are compared to the Hydrus-1D predictive modeling data. The results are used to evaluate the capillarity in soils and to design soil constructions with capillary barriers. [ABSTRACT FROM AUTHOR]

In this study, permeability, particle size distribution of the sandy soils and collected data from several research studies were analyzed and modeled using Vipulanandan p–q model and the results of prediction were compared with the Fredlund and Logistic Growth models used in the literature. The Vipulanandan p–q model was modified and used to represent the particle size distribution of soils. The Vipulanandan p–q model parameters were correlated very well to various soil properties such as the diameter in the particle size distribution curve corresponding to 10%, 30%, 60%, and 90% of finer (d10, d30, d60, and d90 respectively), mean particle size the diameter in the particle size distribution curve corresponding to 50% finer (d50), and fines content (F%). The range of particle sizes investigated in this study was 0.14–0.94 mm, 0.075–1.76 mm, and 0.15–3.59 mm for the d10, d30, and d60, respectively. Also, from the Vipulanandan p–q model parameter, the permeability of the soils have been predicted successfully. A current study also had quantified the lower groutability limit based on the d50 and the Vipulanandan p–q model parameters. The relationship between fines content and d50 were also generalized using the Vipulanandan p–q model to quantify the upper and lower groutability limits for sandy-soils. [ABSTRACT FROM AUTHOR]

Soil structural traits provide links between soil structure and ecosystem functioning. The size and stability of soil aggregates are assumed to provide information on aggregate formation and turnover. A standard method to analyse these traits is to determine the mass distribution on sieves. The major drawback of this method is the small size resolution because of a small number of size classes. A promising, yet still unexplored, method for size distribution analysis in soil science, is dynamic image analysis, which foremost allows a much larger diameter resolution and the assessment of both size and shape distributions. The aim of our study was to validate the applicability of dynamic digital image analysis in combination with sonication to characterize the size and shape distribution and the stability of aggregates. We used two different heterogeneous reference materials and three different soil samples with different aggregate stabilities to test this method. The soil samples were chosen based on increasing clay, humus and calcium carbonate contents. The method yielded reproducible results for diameter and shape distributions for both reference materials and soil samples. The most important improvement compared to well‐established methods was the extremely large size resolution. This allows specification of the pattern of diameter‐dependent breakup curves by relating them to specific soil properties. The information on sphericity adds supplementary information on the aggregates released. We found much lower sphericity of 1‐mm aggregates mobilized from topsoil samples formed from the activity of living organisms than aggregates mobilized from subsoil samples formed mainly by physicochemical processes. Highlights: Our aim was to validate dynamic digital image analysis to characterize soil aggregates.Dynamic image analysis allows high resolution and shape analysis compared to established methods.The method yielded reproducible results for diameter and shape distributions.We established high‐resolution disruption patterns of aggregates enabling new approaches in future research. [ABSTRACT FROM AUTHOR]

The aim of this paper was to characterize soil particle-size distribution (PSD) of in the middle part of young glacial Łyna River valley in relation to parent materials, soil forming processes and slope position. The study comprised rusty soils, arenosols, clay-illuvial soils, colluvial and alluvial soils located in four slope position: summit / midslope, footslope / toeslope, upper and lower part of floodplain. In order to describe the sedimentological environment and possible heterogenity of the soil formations, sedimentological and granulometric indices were calculated. The relationships between soil fractions in A horizons and environmental variables (slope position and depth of A horizon) were determined using principal component analysis (PCA). The studied soils were poorly sorted with various values of skewness of granulometric distribution (symmetrical, fine and very fine skewed) and kurtosis (mainly very leptokurtic). The value of mean grain diameter was decreasing with slope position which may suggest high dynamics and energy of sedimentological environment in the middle part of Łyna River valley. The analysis of granulometric indices revealed that colluvial deposits were the most homogenous and alluvial formations were the most heterogenous. The results of the statistical analysis showed a positive correlation of the amounts of clay and silt fractions with depth of A horizons. The factor responsible for variability of these fractions was the position on the slope. The A horizons in soils located at the summit and footslope had the highest amounts of sand fractions. While significant increase in the share of finer fractions in soils located in the floodplain was noted. [ABSTRACT FROM AUTHOR]

We address the problem of stochastic simulation of soil particle-size curves (PSCs) in heterogeneous aquifer systems. Unlike traditional approaches that focus solely on a few selected features of PSCs (e.g., selected quantiles), our approach considers the entire particle-size curves and can optionally include conditioning on available data. We rely on our prior work to model PSCs as cumulative distribution functions and interpret their density functions as functional compositions. We thus approximate the latter through an expansion over an appropriate basis of functions. This enables us to (a) effectively deal with the data dimensionality and constraints and (b) to develop a simulation method for PSCs based upon a suitable and well defined projection procedure. The new theoretical framework allows representing and reproducing the complete information content embedded in PSC data. As a first field application, we demonstrate the quality of unconditional and conditional simulations obtained with our methodology by considering a set of particle-size curves collected within a shallow alluvial aquifer in the Neckar river valley, Germany. [ABSTRACT FROM AUTHOR]

Collapsing gully erosion is one of the most remarkable natural hazards in hilly granitic region of southern China. However, there have been few studies examining the changes of soil particle-size distribution (PSD) associated with soil profiles of the collapsing gullies. In recent years, the fractal method has become a new one to estimate soil structure. It has been proved to be a useful tool to examine soil properties and the relationships with other eco-environmental factors. To study the fractal dimension ( D) of soil PSD in soils within different weathering profiles (surface layer, red soil layer, sandy soil layer and detritus layer) and its relationships with PSD and soil properties, we conducted an experiment on four collapsing gullies in four counties (Tongcheng County, Gan County, Anxi County and Wuhua County, labeled as TC, GX, AX and WH, respectively) in the hilly granitic region of southern China. The results showed that different weathering profiles exhibited a significant effect on soil physical-chemical properties and PSD. With the fall of weathering degree (from surface layer to detritus layer), as a result, SOM indicated sharp decrease, bulk density first increased sharply and then declined slightly, the finer soil particles (silt and clay) decreased, and especially the clay contents declined noticeably, whereas the gravel and sand contents increased considerably. D values varied from 2.883 to 2.597 of TC, 2.880 to 2.727 of GX, 2.921 to 2.644 of AX and 2.845 to 2.708 of WH, respectively, finer textures giving greater D values. The D values in the sandy soil layers and detritus layers were lower than those in the surface layers and red soil layers. The linear regression analyses showed that D was remarkable negatively correlated with gravel and sand content and positively correlated with clay contents, SOM. The second-degree polynomial equation was more adequate to describe the correlations between D and soil PSD. The results of this study revealed that fractal dimension can be used to characterize the soil grain-size characteristics and was regarded as an informative indicator for reflecting the weathering degree of different weathering profiles of the collapsing gullies in the hilly granitic region. [ABSTRACT FROM AUTHOR]

The specific surface area (SSA) of a soil is crucial for the interface of ions and water molecules with the soil particles. Therefore, many physical and chemical properties of a soil are determined using its total SSA. Measurement of SSA is time-consuming and laborious, and its estimation using pedotransfer functions is therefore preferred. The objectives of this study were to: (1) analyze the pore–solid interface fractal dimension (D) in soils with different textures from thesouthern part of Iran using estimated improved particle-size distribution (PSD) from the soil primary particles, i.e. clay, silt and sand; (2) develop a multivariate pedotransfer function to estimate D based on PSD; and (3) develop a multivariate pedotransfer function to link the values of D to the SSA. As a result, two pedotransfer functions are presented for estimation of D and SSA. To estimate SSA, the value of D is first obtained using the presented pedotransfer function and these estimated D values are then used in another pedotransfer function to estimate SSA. The pedotransfer functions were validated and it is concluded that they are able to predict the values of D and SSA accurately. [ABSTRACT FROM PUBLISHER]

Mathematical models employing textural data are commonly used for the estimation of the particle-size distribution (PSD) curve. In this study, two models were used: (1) the model proposed by Fredlund et al. (2000) (F model), and (2) the model proposed by Skaggs et al. (2001) later modified by Fooladmand and Sepaskhah (2006) (FS model). Comparison of the results obtained by these two models, applied for 30 soils from the south of Iran, showed that the F model was better when the model parameters were determined by setting minimum differences between the measured and estimated PSD curve. Also, three equations based on soil textural data were derived for estimating parameters of the F model, and these equations were used to estimate the PSD curve. The results showed that for 10 independent soils from the south of Iran and 50 soils from the UNSODA database, the FS model was better than the F model based on three new derived equations. Therefore, the FS model can be safely used to estimate the PSD curve with different soil textures; however, the F model is appropriate for representation of the measured PSD curve. [ABSTRACT FROM PUBLISHER]

• Complexity of loess formations: polyciclic and polygenetic loess-derived soils. • Profile description, soil particles color, shape and size distribution. • Evidences of size-dependant wind transport, loess depositions of different sources. • Fine grained nature of loess, in agreement with major alluvial origin. • Differences in particle size distributions pointing to weathering pathways. The multiplicity of units present in a single loess bed greatly complicates the reconstruction of the history of polycyclic loess-derived soils. The present study implemented a combination of techniques to characterize different depositional events in a pedogenized loess formation of North-Western Italy. Field morphological observations, laboratory Particle Size Distribution (PSD) analyses, and single-grain image processing techniques were applied. Five different loess depositions, or cycles, were distinguished in the field. Laser PSD curves highlighted the fine nature of the studied loess, which stood out even in comparison to similar Italian loess-derived soils. All PSD functions showed a tri/bimodal distribution with a dominant peak at 8–14 μm, wider in younger depositions. The second most relevant peak, at 0.5–4 μm, displayed a greater intensity in older cycles where it also fell in correspondence of slightly bigger particles. The fine-grained nature of the loess was read as a sign of its alluvial origin, therefore the Po plain has been addressed as the source of the material. This hypothesis was supported by evidence of a dominant SE-to-NW paleo-wind direction, proved by the spatial trends of the coarse and fine silt fractions. The typical aeolian size-dependant depositional trait of one of the cycles (IV) was however opposite to that of the other four loess depositions. Therefore, the source of this material was attributed to a site North of the study area where, right behind the Lanzo ultramafic massif, an ice lobe stretched during the Last Glacial Maximum (LGM). Image analysis supported this hypothesis: as the loess grains of cycle IV were significantly darker colored than the others, this would agree with the provenance from an ultramafic source. In conclusion, the variety of applied techniques allowed us to combine different pieces of information in order to assess the physical and morphological properties of the studied loess-derived soils, trying to determine the most probable sources of the material and the weathering pathways. [ABSTRACT FROM AUTHOR]