Characterization of oil shale residue and rejects from irati formation by electron paramagnetic resonance

In this study, sedimentary organic matter of oil shale rejects, calschist, shale fine and the so called retorted shale from Irati formation was characterized. EPR was used to analyse the samples regarding loss of signal in g = 2.003 associated to the organic free radical with the calcined samples and washing with hydrogen peroxide. The radical signal was detected in all samples, however, for the calschist and shale fine samples another signal was identified at g = 2.000 which disappeared when the sample was heated at 400 ºC. Hydrogen peroxide washing was also performed and it was noted that after washing the signal appeared around g = 2.000 for all samples, including retorted shale, which might be due to the quartz E1 defect

Densidade de agregados de solo: Uso da balança de Jolly em aulas de física experimental para educação em ciência do solo

A densidade do solo (D s ) representa uma importante propriedade física desse meio poroso sendo muitas vezes utilizada como índice de qualidade do solo. Existem diferentes métodos de medida de D s: anel volumétrico (MAV), torrão parafinado (MTP) e atenuação de raios gama. Em aulas de Física Experimental, no módulo Hidrostática e Hidrodinâmica, geralmente são efetuadas medidas de densidade de materiais sólidos, cujos valores de densidade são conhecidos. Devido às dificuldades em se trabalhar com amostras de solo em laboratórios de Física Experimental, na maior parte das vezes os estudantes acabam efetuando medidas de D s somente em cursos mais específicos de sua graduação. Um aparato geralmente utilizado em medidas de densidade em laboratórios de Física Experimental é a balança de Jolly (MBJ). Nesse trabalho tal aparato foi empregado em medidas de densidade de agregados (D A g g ) de solo. Amostras de agregados parafinados com diferentes volumes foram utilizadas no estudo. Os resultados obtidos mostraram concordância nos valores de D A g g utilizando os métodos do MAV e MBJ. Desta forma, a ideia desse trabalho é mostrar a viabilidade do uso da balança de Jolly em medidas de D A g g e sua aplicabilidade para estudar importantes conceitos referentes à estrutura do solo em aulas de Física Experimental.</jats:p

Characterization of changes in soil porous system by gamma-ray tomography

AbstractIn this study the use of a first generation computed tomography (CT) scanner to evaluate changes in total porosity and bulk density of a porous medium (a soil sample) submitted to wetting and drying (W–D) cycles is presented. In nature, soils are commonly submitted to W–D cycles as they are exposed to the hydrologic cycle. Also, a large number of procedures conducted at laboratory levels frequently expose soils to W–D cycles. The methodology using the CT technique was applied to investigate a Brazilian clayey soil submitted to consecutive W–D cycles. The obtained results showed that the use of CT permitted a detailed evaluation of important changes in soil bulk density and total porosity due to these cycles, something that cannot be achieved by the traditional methods used to investigate these physical parameters

Radiation attenuation properties based on the quantification of soil components using the Rietveld Method

We propose the use of X-ray diffraction associated with Rietveld Method (RM-XRD) for soil components quantification aiming at evaluating photon attenuation parameters (total and partial attenuation coefficients (µ), effective atomic number (Zeff), effective electron density (Nel) and cross-sections per atom (σa) and per electron (σe)). The XCOM computer code was utilized to calculate these parameters. The X-ray fluorescence spectroscopy (XRF) technique was used as reference for the quantification of soil components. Good agreement was found between XRF and RM-XRD for photons ranging from medium to high energies. Photons of low energy (<0.1 MeV) presented slight differences between these two methods. Keywords: X-ray diffraction, X-ray fluorescence spectroscopy, XCOM computer code, Mass attenuation coefficient, Cross-section

Soil organic matter humification under different tillage managements evaluated by Laser Induced Fluorescence (LIF) and C/N ratio

AbstractIn this work is presented the use of the C/N ratio and the Laser Induced Fluorescence (LIF) spectroscopy for determining the humification of soil organic matter (SOM) in an Oxisol under three different long-term tillage managements (no-tillage (NT), reduced tillage (RT) and conventional tillage (CT)). Humification of SOM was evaluated in the soil and its fractions (clay<2μm, silt 2–20μm, sand 20–1000μm). The obtained results show that lower SOM humification was observed in soil under NT, mainly at the surface (0–5cm). In CT, SOM humification values maintained constant for all investigated depths (0–5, 5–10, 10–15 and 15–20cm). Also, clay was the soil fraction that exhibited the lesser humification of SOM. Based on the obtained results it can be said that NT favors the accumulation of SOM on its surface, increasing aggregate stability and presenting samples with lower humification indexes. These results indicate a larger availability of nutrients for the plants in this management