Soil Pore Network Complexity Changes Induced by Wetting and Drying Cycles-A Study Using X-ray Microtomography and 3D Multifractal Analyses.

Soils are dynamic and complex systems in their natural state, which are subjected to profound changes due to management. Additionally, agricultural soils are continuously exposed to wetting and drying (W-D) cycles, which can cause modifications in the complexity of their pores. Thus, we explore how successive W-D cycles can affect the pore network of an Oxisol under contrasting managements (conventional tillage-CT, minimum tillage-MT, no tillage-NT, and secondary forest-F). The complexity of the soil pore architecture was evaluated using a 3D multifractal approach combined with lacunarity, Shannon's entropy, and pore geometric parameters. Our results showed that the multifractal approach effectively identified and quantified the changes produced in the soil pore architecture by the W-D cycles. The lacunarity curves revealed important aspects of the modifications generated by these cycles. Samples under F, NT, and MT suffered the most significant changes. Pore connectivity and tortuosity were largely affected by the cycles in F and NT. Our findings demonstrated that the 3D geometric parameters and normalized Shannon's entropy are complementary types of analysis. According to the adopted management, they allowed us to separate the soil into two groups according to their similarities (F and NT; CT and MT).

Can we predict the occurrence of COVID-19 cases? Considerations using a simple model of growth.

This study aimed to present a simple model to follow the evolution of the COVID-19 (CV-19) pandemic in different countries. The cumulative distribution function (CDF) and its first derivative were employed for this task. The simulations showed that it is almost impossible to predict based on the initial CV-19 cases (1st 2nd or 3rd weeks) how the pandemic will evolve. However, the results presented here revealed that this approach can be used as an alternative for the exponential growth model, traditionally employed as a prediction model, and serve as a valuable tool for investigating how protective measures are changing the evolution of the pandemic.

Porosity distribution by computed tomography and its importance to characterize soil clod samples.

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 100cm(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.

Pore system changes of damaged Brazilian oxisols and nitosols induced by wet-dry cycles as seen in 2-D micromorphologic image analysis

Soil pore structure characterization using 2-D image analysis constitutes a simple method to obtain essential information related to soil porosity and pore size distribution (PSD). Such information is important to infer on soil quality, which is related to soil structure and transport processes inside the soil. Most of the time soils are submitted to wetting and drying cycles (W-D), which can cause important changes in soils with damaged structures. This report uses 2-D image analysis to evaluate possible modifications induced by W-D cycles on the structure of damaged soil samples. Samples of three tropical soils (Geric Ferralsol, GF; Eutric Nitosol, EN; and Rhodic Ferralsol, RF) were submitted to three treatments: 0WD, the control treatment in which samples were not submitted to any W-D cycle; 3WD and 9WD with samples submitted to 3 and 9 consecutive W-D cycles, respectively. It was observed that W-D cycles produced significant changes in large irregular pores of the GF and RF soils, and in rounded pores of the EN soil. Nevertheless, important changes in smaller pores (35, 75, and 150 µm) were also observed for all soils. As an overall consideration, it can be said that the use of image analysis helped to explain important changes in soil pore systems (shape, number, and size distribution) as consequence of W-D cycles.

A caracterização da estrutura do solo usando a análise de imagens bidimensionais (2-D) constitui um método simples na obtenção de informações essenciais relacionadas com a porosidade do solo e a distribuição do tamanho de poros. Tal informação é importante para obter dados sobre a qualidade do solo, a qual está diretamente ligada à sua estrutura e aos processos de transporte que ocorrem no seu interior. Na maior parte do tempo os solos são submetidos a vários ciclos de umedecimento ("wetting") e secamento ("drying") (W-D) que podem causar importantes mudanças em solos que possuem estruturas danificadas. Neste estudo foi usada a análise de imagens em 2-D na avaliação de possíveis modificações devido a vários ciclos de W-D na estrutura de amostras de solo danificadas.Três solos diferentes em textura (Latossolo vermelho-amarelo distrófico - LVAd; Nitossolo vermelho eutrófico - NVe, Latossolo vermelho distrófico - LVd) foram submetidos a três diferentes tratamentos: 0WD, amostras controle não submetidas a nenhum ciclo de W-D; 3WD e 9WD, amostras submetidas a 3 e 9 ciclos consecutivos de W-D, respectivamente. Foi observado que os ciclos de W-D produziram mudanças significativas nos poros grandes irregulares dos solos LVAd e LVd e nos poros arredondados do NVe. Importantes mudanças nos poros de 35 até 150 µm foram observadas para todos os solos estudados. A partir dos resultados obtidos pode ser dito que o uso da análise de imagens auxiliou com sucesso na explicação de variações no sistema poroso (formato, número e distribuição de tamanho dos poros) devido aos ciclos de W-D para todos os solos analisados.