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Gamma-ray computed tomography (CT) was employed to study the soil quality of clod samples used to investigate porosity ( ϕ ). Samples with volumes varying from 50 to 100 cm 3 were collected from the soil surface. 2D CT images were obtained with millimetric resolution. Porosity distribution analyses were carried out to infer the soil clod structure. Results obtained provided a new insight on the variability of internal clod structure due to the large amount of data analyzed, information that is not provided by traditional methods used in physics applied to soil. [ABSTRACT FROM AUTHOR]

Soil vestiges might provide information about a crime scene. The Rietveld method with X-ray diffraction data ( RM- XRD) is a nondestructive technique that makes it possible to characterize minerals present in the soils. Soil clays from the metropolitan region of Curitiba (Brazil) were submitted to DCB treatment and analyzed using XRD with CuKα radiation in the step-scan mode (0.02° 2θ/5 s). The GSAS+ EXPGUI software was used for RM refinement. The RM- XRD results, together with the principal component analysis ( PCA) (52.6% total variance), showed the kaolinite predominance in most analyzed samples and the highest quartz contents in 'site 1.' Higher anatase, and gibbsite and muscovite contents influenced discrimination, mainly in 'site 3' and 'site 1,' respectively. These results were enough to discriminate clays of four sites and two horizons using a reduced amount of sample showing that the technique can be applied to the investigation into soil vestiges. [ABSTRACT FROM AUTHOR]

The rapid, simple and accurate determination of soil quality indicators is fundamental for improvements in precision agriculture and consequently in production efficiency. The objectives of this study were to determine the organic matter (OM) and total organic carbon (TOC) concentrations in agricultural soil and to discriminate soil provenance by energy-dispersive X-ray fluorescence (EDXRF) combined with principal component analysis and partial least square regression. The conventional methods used for the determination of OM and TOC concentrations are the gravimetric and Walkley–Black methods, respectively. Figures of merit such as sensitivity, detection and quantification limits, accuracy and precision were evaluated. Samples were differentiated by their provenance, and the quality of the prediction model shows that EDXRF combined with multivariate analysis is a promising methodology to fulfil the lack of rapid and accurate analytical methods for the assessment of OM and TOC concentrations in agricultural soils. [ABSTRACT FROM AUTHOR]

Abstract 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−1, 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 via both quantitative and qualitative analyses. On the other hand, liming did not affect pore connectivity under any of the circumstances. Highlights • Surface liming improved soil aggregation by increasing the mean weight diameter. • Smaller soil aggregates present higher percentage of calcium due to liming. • Liming effects on soil physical properties were stronger for smaller aggregates. • In these small aggregates, liming decreased porosity and increased tortuosity. • Liming provided a more homogeneous intra-aggregate pore space. [ABSTRACT FROM AUTHOR]

Abstract: The atomic force microscopy (AFM) is a technique for direct three dimensional measurements of the mineral structure in nanometric scale. In the literature, there are studies which approach the characterization of surfaces in atomic scale through AFM, such as humic substances and minerals. However, the number of studies aiming to characterize the clay fraction minerals in soil using this technique is not representative. In this study, AFM was employed to characterize the clay fraction morphology and microtopography in the surface layer of a Rhodic Ferralsol in Brazil, and X-ray diffraction (XRD) together with the Rietveld Method (RM) to characterize and quantify the main minerals. Images analyzed presented particles from 3 to 25nm. Through XRD and RM mineralogical analysis, the minerals found in higher amounts from the most to the least were, gibbsite, kaolinite, hematite, anatase, goethite, magnetite, calcite, vermiculite and rutile. AFM images made it possible to identify, by observing the height and shape, the particles that corresponded to kaolinite, goethite and gibbsite. This study shows the potential of the AFM technique to measure clay in nanometric scale and the possible identification of minerals present in the clay fraction with the use of XRD and RM. [Copyright &y& Elsevier]