The occurrence of iron‐rich rocks in some areas makes possible the formation of duricrusts in positions from the relief tops to the slopes and valley bottoms, as is the case of the Quadrilátero ...Ferrífero (QF—‘Iron Quadrangle’) in the Brazilian Atlantic Plateau. This study aimed to analyse these materials in the Late Pleistocene fluvial archives of the QF to contribute to the understanding of the complex processes involved in the evolution of surface coverage in tropical regions. The results showed an essential external iron source for the Fe‐cemented alluvium, that is, they are ferricretes. Two ferricrete facies were identified: plate‐shaped and conglomeratic. They are characterised by the infilling of a primary porous system with crystalline and amorphous ferruginous phases or grain coatings by ferruginous materials. In plate‐shaped ferricretes, the size of the cemented grains differentiates the identified subtypes. Conglomeratic ferricretes can be subdivided into ferruginous and aluminous, and feature two types of cementing microstructures: septary and microlaminar. The results of the X‐ray diffraction analysis of the conglomeratic ferricretes highlight the strong presence of goethite (more common) and hematite. The chemical composition corroborated the mineralogical analysis, with the septa having an average iron‐rich composition. Aluminous conglomeratic ferricretes also occur and are the oldest in the area; their cement is composed mainly of gibbsite. Thus, it can be considered (i) a possible past source area of aluminous sediments or (ii) the in situ deferruginisation of a first level of ferricretes. A certain granulometric control in both ferricrete facies reinforces the importance of transport and deposition during ferricrete genesis. However, the cementing of sediments under supergene conditions and their microstructural variety suggest that their formation and evolution also occurred as a result of lateritic processes. Furthermore, the ferricretes revealed integration with the regional relief evolution, and the conglomeratic ones may be associated with lower rates of drainage incisions in some valleys.
Conglomeratic ferricretes (CF) present the infilling of a primary porous system by crystalline and amorphous ferruginous phases or grain coatings by ferruginous materials. Aluminous CF in older fluvial levels. Ferruginous CF occurs in younger fluvial levels. Changes in source areas of sediments or deferruginisation process must be considered.
•Penguins’ colonies account for a high degree of soil phosphatization and chemical weathering.•Penguins are key drives of P and organic matter sea land transfers in Maritime Antarctica.•High ...organic-P contents in soils indicate penguins directly influencing the landscape evolution following glacial retreat.•Penguins promote changes in the ecological succession of ice-free areas of Maritime Antarctica.
Extensive areas of penguins’ nesting (Pygoscelis sp.), on ice-free areas, account for vast deposits of organic matter-rich guano in maritime Antarctica. One such area, at Harmony Point, currently houses different penguin colonies with extensive and unique ornithogenic soils, where phosphatization is the key soil-forming process. We sought to enhance the knowledge of phosphatization process, products, cycles, and phosphorus (P) forms in these unusual soils. We compared ornithogenic and non-ornithogenic soils, based on advanced chemical, micromorphological and mineralogical analyses of samples of guano and phosphate biocrusts, complete with P and OM fractionation. Ornithogenic soils have the organic P-pool as the largest phosphorous compartment, followed by varying P-Ca forms. In contrast, soils unaffected by phosphatization showed a high inorganic P-pool. Penguin guano is enriched with P, Ca, K, Cu, Zn, C and N. The phosphatic biocrusts are composed of struvite and hydroxyapatite, forming a gradient of phosphate forms. We recognized three different phosphatization environments, namely (i) present-day marine birds’ rookeries, (ii) adjacent zone of rookeries and (iii) abandoned rookeries. Geomorphological evolution of the coastal areas, by Holocene glacier retreat, resulted in the changing location of penguin colonies, resulting in a larger area and varying ages of phosphatization, forming ornithogenic soils with contrasting evolution degrees. Abandoned areas have greater vegetation growth, with higher diversity.
ABSTRACT
There has long been a discussion about the effects of soil management on its structure. Since changes can occur due to management and time of use, more accurate assessments can be achieved ...if carried out in long-term experiments. This study investigated the long-term effects of soil management on the physical quality of a Cerrado Oxisol (Latossolo Vermelho), focusing on microstructural changes. Micromorphology and computed tomography techniques were used to assess the soil's microstructure. The study compared areas under long-term and different soil management practices, including disc plowing, no-tillage, and disc harrow+subsoiler. A native Cerrado area was considered as the reference. Micromorphology revealed some changes in the pedological features of soil aggregates, but the granular structure showed good resistance even after two decades of use and management. It also indicated a decrease in larger pores and an increase in the surface soil layer micropores for the disc plowing and no-tillage treatments. These results were consistent with traditional laboratory evaluations of soil porosity. Computed tomography was limited due to increased soil bulk density in the cultivated treatments, but it showed potential for assessing soil porosity and pore connectivity. We concluded that micromorphology effectively identifies microstructural changes in Oxisols with small and strong granular structures, and the granular soil aggregates displayed resilience even after long-term management. The micromorphometric evaluation corroborates with traditional methods and suggests loss of pores associated with the disc harrow+subsoiler treatment.
Toposequence: What are we talking about? Alves, Grace Bungenstab; Oliveira, Fábio Soares de; Silva, Artur Henrique Nascimento da ...
Revista Brasileira de Ciência do Solo,
01/2024, Letnik:
48
Journal Article
Recenzirano
Odprti dostop
ABSTRACT The term toposequence, proposed to designate a lateral succession of soils on a slope due to the influence of topography, began to be used differently over time, distancing itself from its ...original concept. Here, we discuss how this concept has been used since its inception. We carried out bibliometric analyses of publications in the database available on the Web of Science since 1900. Three main approaches and related concepts, explicit or not, one at a regional scale and two others at a local scale were identified. From this analysis, we suggest: a) when the approach is regional, the term geomorphic surface or position in the landscape should be used to address the spatial distribution and genetic implications of soils at this scale; b) when dealing with series/sequences of soils on slopes for mapping purposes or discontinuous profiles that emphasize taxonomic classification, the term catena should be used; c) when the determining factor of the soil sequence is climatic, biotic, lithological, chronological, the corresponding term climo-, bio-, litho- or chronosequence should be used; d) when dealing with a lateral succession of horizons in the continuum on slopes, resulting from the influence of topography on soil formation, which may reflect the soil contribution to the model evolution, only in this case should the term toposequence be used, returning to its original concept.
ABSTRACT Soil evolves in landscapes in a natural process in which soil properties are gradually transformed. However, the transformation of argic to ferralic horizons in basic rock-derived soils ...under tropical conditions is poorly understood. Depending on the position of the soil profiles in landscape, evidence of pedogenetic transformation between different horizons might indicate the formation and destruction of aggregates with shiny faces. This study aimed to determine pedogenetic changes in basic rock-derived profiles in a toposequence, because soils derived from mafic rocks are not abundant in the study region (Pinheiral, Rio de Janeiro State, Brazil). Trenches were dug at the summit (P1), upper (P2), middle (P3), and lower (P4) thirds along the toposequence. The morphological, physical, chemical, mineralogical, and micromorphological properties of the profiles were characterized, and a weathering index was calculated from X-ray fluorescence element values. All profiles had chemical and physical properties indicating an advanced degree of weathering resulting from the parent material and tropical climate conditions. In P1 and P4 that were classified as Nitossolos, the most evident pedogenetic processes were ferralitization and nitidization, due to the advanced degree of weathering, accumulation of oxyhydroxides and kaolinite in the horizons, and formation of textural pedofeatures by mechanical-hydric stress and evidence of the illuviation process. Profiles P2 and P3 revealed a ferralitization process and were classified as Latossolos. Absence of shiny macromorphological ped faces in some Bw horizons, and their micromorphological coexistence in Bt and Bw horizons within the same profile were associated with the transformation of the blocky into a granular microstructure, suggesting argic-ferralic horizon transformation.
Measures of traits are the basis of functional biological diversity. Numerous works consider mean species-level measures of traits while ignoring individual variance within species. However, there is ...a large amount of variation within species and it is increasingly apparent that it is important to consider trait variation not only between species, but also within species. Mammals are an interesting group for investigating trait-based approaches because they play diverse and important ecological functions (e.g., pollination, seed dispersal, predation, grazing) that are correlated with functional traits. Here we compile a data set comprising morphological and life history information of 279 mammal species from 39,850 individuals of 388 populations ranging from −5.83 to −29.75 decimal degrees of latitude and −34.82 to −56.73 decimal degrees of longitude in the Atlantic forest of South America. We present trait information from 16,840 individuals of 181 species of non-volant mammals (Rodentia, Didelphimorphia, Carnivora, Primates, Cingulata, Artiodactyla, Pilosa, Lagomorpha, Perissodactyla) and from 23,010 individuals of 98 species of volant mammals (Chiroptera). The traits reported include body mass, age, sex, reproductive stage, as well as the geographic coordinates of sampling for all taxa. Moreover, we gathered information on forearm length for bats and body length and tail length for rodents and marsupials. No copyright restrictions are associated with the use of this data set. Please cite this data paper when the data are used in publications. We also request that researchers and teachers inform us of how they are using the data.
PURPOSETo investigate the influence of the etching strategy of universal adhesives on bond degradation to sound and artificially-induced caries-affected dentin. MATERIALS AND METHODSThe universal ...adhesives (Scotchbond Universal Adhesive; All-Bond Universal; Prime&Bond Elect) and adhesives used as controls (Adper Single Bond 2 and Clearfil SE Bond) were applied to sound and artificially-induced caries-affected bovine dentin. Microtensile bond strength was evaluated immediately (24 h) and after one year of water storage (1 year). Representative specimens were also prepared to assess nanoleakage. Bond strength data (MPa) were analyzed using three-way ANOVA and post-hoc Tukey's test (α = 0.05), considering each substrate separately. RESULTSBonding degradation was observed for all universal adhesives on caries-affected dentin, irrespective of the etching strategy. On sound dentin, bonding degradation was observed when adhesives were used on the etch-and-rinse strategy. CONCLUSIONThe universal adhesives were not capable of maintaining bond stability over time on caries-affected dentin. The self-etch strategy seems better able to maintain the durability of adhesive interfaces created on sound dentin.
•Compositional and textural control in the typology of ferruginous duricrusts.•Formation of platy and massive types of ferruginous duricrust.•Massive duricrust associated with ancient diamond ...mines.•Evolution of ferruginous duricrusts from alteromorphization and laterization processes.
The Espinhaço Range is the scene of a long history of exposure to chemical weathering and erosion processes since the Cretaceous. As a result, ferruginous duricrusts can be considered as the fingerprint of the long-term surface process and may provide us critical clues about changes in paleo-environmental features during the Cenozoic. In addition, specifically for the Diamantina plateau, located in the state of Minas Gerais (Brazil), there is great interest in studying the duricrusts of the Espinhaço Range, because they are associated with diamond mining, explored since the eighteenth century and which gave its name to the region. Even so, few studies have contributed to understanding their formation and morphological diversity. Mineralogical, geochemical, and micromorphological studies were undertaken to understand the processes involved in the formation of the two representative types of ferruginous duricrust, linked to phyllites of Espinhaço Supergroup: platy and massive types. The platy duricrust develops from the weathering of a banded ilmenite-hematite phyllite where the alteromorphization of its compositional banding and original foliation leads to the formation of an isalteritic duricrust. The massive duricrust, associated with diamond mining, is genetically linked to a quartz-phengite phyllite. Both duricrust profiles show relative enrichment in Fe and P and depletion of the other major elements compared to the saprolite, however, the iron concentration was 10 times greater in the massive than the platy duricrust. The REEs show similar distribution patterns with preferential leaching in both duricrusts. The compositional and textural variation of the phyllite in the Diamantina Plateau leads to the distinct evolution of two representative duricrusts profiles. The mineralogical, micromorphological, and geochemical analyses reinforce the lithological control in the formation of these two different types of ferruginous duricrusts in the study area, located in similar topographic and climatic conditions.
•The chemical weathering intensity in Maritime Antarctica is modeled.•A geophysical survey and lithological characteristics as input data.•Proximal geophysical sensors and terrain attributes are ...combined for modeling.•Use of leave-one-out-cross-validation method in modeling.•Periglacial processes control the distribution of geophysical variables.
The chemical weathering intensity in Antarctica is underestimated. As the chemical weathering intensity increases, hydrological, geochemical and geophysical changes occur in the different environmental spheres and at their interfaces through reactions and energy flows. Thus, once chemical weathering rates are understood and estimated, they can be used to predict and assess changes and trends in different environmental spheres. Few studies on the chemical weathering intensity have been performed in Antarctica. We used radiometric and magnetic properties associated with terrain attributes and the chemical degree of alteration of the igneous rock to model the chemical weathering intensity in Maritime Antarctica by using machine learning. Then, we related the chemical weathering intensity and geophysical variables with periglacial processes. To do this, gamma-spectrometric and magnetic readings were carried out using proximal-field sensors at 91 points located on different lithologies in a representative area of Maritime Antarctica. A qualitative analysis of chemical alteration for the different lithologies was carried out based on field observations and rock properties, and the levels of the chemical weathering degree were established. The geophysical data associated with terrain attributes were used as input data in the modeling of the weathering intensity. Then, the levels of the rock weathering degree were used as the “y” variable in the models. The results indicated that the C5.0 algorithm had the best performance in predicting the weathering intensity, and the most important variables were eTh, 40K, 40K/eTh, 40K/eU, the magnetic susceptibility and terrain attributes. The contents of radionuclides and ferrimagnetic minerals in different lithologies, concomitantly with the intensity at which chemical weathering occurs, determine the contents of these elements. However, the stability and distribution of these elements in a cold periglacial environment are controlled by periglacial processes. The chemical weathering intensity prediction model using gamma-spectrometric and magnetic data matched the in situ estimate of the chemical degree of alteration of the rock. The pyritized andesites showed the highest intensities of weathering, followed by tuffites, diorites, andesitic basalts and basaltic andesites, and the lowest weathering intensity was shown by undifferentiated marine sediments. This work highlighted the suitability of using machine learning techniques and proximal-field sensor data to study the chemical weathering process on different rocks in these important and inhospitable areas of the cryosphere system.
Primary aluminum production is an uninterrupted and complex process that must operate in a closed loop, hindering possibilities for experiments to improve production. In this sense, it is important ...to have ways to simulate this process computationally without acting directly on the plant, since such direct intervention could be dangerous, expensive, and time-consuming. This problem is addressed in this paper by combining real data, the artificial neural network technique, and clustering methods to create soft sensors to estimate the temperature, the aluminum fluoride percentage in the electrolytic bath, and the level of metal of aluminum reduction cells (pots). An innovative strategy is used to split the entire dataset by section and lifespan of pots with automatic clustering for soft sensors. The soft sensors created by this methodology have small estimation mean squared error with high generalization power. Results demonstrate the effectiveness and feasibility of the proposed approach to soft sensors in the aluminum industry that may improve process control and save resources.
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