ABSTRACT: A set of attributes endows the soils with distinctive characteristics and astute understanding is required in order to formulate suitable strategies for soil management. The aim of this study was to physically, chemically and mineralogically characterize samples of the main soil classes in Minas Gerais, Brazil, determine the point of zero salt effect (PZSE) and the point of zero charge (PZC), and ascertain the correlation between these factors and soil attributes. The soils evaluated presented different textural classes ranging from loamy sand (Entisol) to very clayey (some Oxisols and Ultisols). The soils differed substantially in terms of fertility, presenting a range from dystrophic (low fertility, base saturation < 50 %) to eutrophic character (fertility, base saturation ≥ 50 %), even within the same soil class, such as the Oxisols, which suggests the concurrence of the parent material. Highly weathered soils are predominant in Minas Gerais and these soils are composed predominantly of kaolinite, gibbsite, goethite and hematite. Traces of hydroxy-Al interlayered vermiculite and illite were also found in the Oxisols, Ultisols and Inceptisols. A correlation between the PZSE and the PZC in the A horizon was observed. A high degree of correlation was observed between the PZC and the exchangeable aluminum and the ratio of iron obtained by ammonium oxalate and dithionite-citrate (Feo/Fed) in both the A and B horizons of soil classes. The results obtained reinforce the importance of knowledge of soil attributes to the adoption of practices such as the management of phosphate fertilization in clayey soils and liming in soils rich in aluminum.

ABSTRACT: Arsenic (As) is a naturally occurring chemical element considered toxic and carcinogenic by health and environmental protection agencies. Studies of As adsorption/desorption behavior in soils are important to predictions of As’ potential mobility in natural systems. The aim of this study was to assess the adsorption of As(V) in soils from Minas Gerais, Brazil, and determine its immobilization rate in order to identify soils with characteristics more favorable to its deployment as an As geochemical barrier. The adsorption experiment was performed using different As concentrations and the data pertaining to the maximum adsorption capacity of As(V) (MACAs) were determined by Langmuir and Freundlich isoterms. The Oxisols, due to their more oxidic mineralogy, especially more gibbsitic, and clayey texture, showed the highest MACAs, followed by Ultisols, Inceptisols, and Entisols. In terms of the desorption of As the Inceptisols were the soils that showed the most As desorption. Both As desorption and mobility was lower in the more oxidic and clayey soils. In all soils, the total amount of As was desorbed in due course, but the As release ratio tended to decrease with the passage of time. In general, soils with higher MACAs did not necessarily show less As desorption. For use as a geochemical barrier, as important as a high adsorption capacity of As by the soil is a low As desorption rate. The increase in As mobility may increase the risks of contaminating the supplies of water. To be a good As geochemical barrier the soil has to be a clayey Oxisol, with relatively high amounts of Fe and Al oxides, especially gibbsite.

ABSTRACT: The Atlantic Forest is one of the most important and yet the most devastated Brazilian biome, occupying in the past the majority of the East Atlantic Coast. Therefore, a detailed knowledge of the soils near the coastal line influenced by this biome is essential for land use and management of these environments. The aim of this study was to acquire a deeper knowledge of the chemistry, mineralogy and genesis of soils in two micro-watersheds of the Atlantic Forest Biome. Eight soil profiles were sampled and described along one transect. Both young and more developed soils exhibit low fertility and low Fe2O3 content. The Oxic Dystrudepts are less dystrophic than the other soils studied and exhibit greater availability of K+, due to the mixing of weathered material and primary minerals. Transitions from shallow to deep soils are more common in rejuvenated landscapes. All soils are kaolinitic (Kt), with low levels of goethite (Gt) and hematite (Hm), and contain secondary 2:1 minerals such as mica (Mi) and, in the youngest soils, hydroxy-interlayered vermiculite (HIV) and interstratified mica-hydroxy-interlayered vermiculite (Mi-HIV). The widespread presence of gibbsite (Gb) in soils, including the Lithic Udifolist, indicates high rates of both pedogenesis and morphogenesis. The gibbsite showed good crystallinity suggesting that climate, terrain and good drainage favored its formation and stability.

ABSTRACT Ferrimagnetic Fe-oxides are important soil components, which are present in most of the agricultural soils of Brazil. Distinction, origin, and assessment of the influence of these minerals on magnetism and geochemistry is a challenge for mineralogists. This study aimed to characterize mineralogically Fe-rich Rhodic Oxisols ( Latossolos Vermelhos ) originating from several mafic rocks in Brazil, and assess the implications on their magnetic and geochemical properties. We present results on magnetic measurements, chemical dissolutions, X-ray diffractometry, Rietveld refinement, Raman, and Mössbauer spectroscopies of Fe-rich Rhodic Oxisols originating from several mafic rocks. They show that magnetite is inherited from the parent material, and its oxidation leads to the formation of maghemite. In the coarse fractions (sand and silt), magnetite and maghemite coexist and are interstratified with hematite, confirmed by Raman spectroscopy. This limited the distinction between magnetite and maghemite by Mössbauer spectroscopy. Maghemite represents the only ferrimagnetic Fe oxide in the clay fraction. The influence of both ferrimagnetic minerals, magnetite and maghemite, on magnetic susceptibility and total content of trace elements is determined by the pedogenic development, even among highly weathered soils. In general, the coarse fractions contribute with most of the total trace element contents, while the clay fraction contributes to trace elements availability and magnetic susceptibility of soils.

ABSTRACT: Fe-rich Oxisols on mafic rocks in Brazil generally have high magnetic susceptibility with high contents of some trace elements. These are taxonomically similar soils; however, differences in magnetic and geochemical properties may affect agricultural or environmental usability and subsequent management. This study investigated the pedogenesis of Fe-rich Oxisols from various parent materials and evaluated the lithogenetic influence on magnetic susceptibility and trace elements contents. Soil samples were collected from Bw horizons in 13 Rhodic Oxisols and a Typic Oxisol developed from several parent materials in Minas Gerais State, Brazil. Soils were analyzed by X-ray diffractometry (XRD) and magnetometry. Soil chemical analyses consisted of sulfuric and total (tri-acid) digestions and selective Fe oxides dissolutions and statistical correlations were determined. Fe-rich Oxisols presented a typical mineralogical composition of highly weathered soils with structural stability. The results confirm the difficulty to identify accurately magnetic minerals in different grain sizes using XRD. However, coarse fractions still exert dominant influence on the magnetic properties of the Fe-rich Rhodic Oxisols. In addition, coarse fractions probably contribute to the enrichment of superparamagnetic particles for the clay fraction. Although highly weathered, Fe-rich Oxisols may have their geochemical attributes still controlled by the parent material, where trace elements seem to be correlated with the magnetic minerals in the coarse fractions. Thus, the natural replacement of some trace elements from soil-solution equilibrium reactions during plant development could be more effective in soils with higher magnetic particles concentrations in the coarse fractions.

ABSTRACT: Evaluating soil geochemical diversity in the Amazon Basin has been a challenge largely because most study sites have been at the edge of the basin and it is difficult to get samples in such a region. Here we show that even among the most weathered soils, physicochemical soil properties express lithology. Our results are based on topsoil samples collected from different locations in minimally disturbed areas in the state of Amazonas, Brazil. Soil properties were measured using methods which are suitable for highly developed soils. The Chemical Index Alteration and Weathering Index of Parker was calculated based on the content of metal(loid)s in soils determined by X-ray fluorescence. Descriptive statistics, Pearson correlation, and Principal Component Analysis (PCA) were performed on data. In general, Amazon rainforest soils are more deeply weathered than soils in other Brazilian biomes and tropical rainforests in Asia and Africa. The high coefficient of variation of metal(loid) contents express pedogenesis and parent material diversity. Correlation analysis indicated that the tri-pentavalent elements are strongly associated with Al and Fe contents in the topsoil. In contrast, mono-divalent elements are correlated with sand and silt fractions. According to PCA, five soil groups with defined geochemical compositions and degrees of weathering could be identified: i) acidic sandy podzolized soils; ii) acidic loamy ferralitic soils with the highest content of tri-pentavalent ions; iii) acidic clayey kaolinitic soils with low metal(loid) contents; iv) acidic loamy kaolinitic soils with low metal(loid) contents; and v) silty neutral 2:1 clay soils. This study is the first effort to analyze the geochemical diversity in Amazon rainforest soils. These data are extremely valuable in determining the geochemical background for these soil types and this region. Geochemical variability can be predicted to some extent by lithology and pedogenesis, which can be applied to define the sampling required in future studies.

ABSTRACT Despite the considerable amount of information on the mineralogical characteristics of pedogenic Fe oxides in Brazilian soils, there are few studies on Fe-rich soils developed from mafic rocks with taxonomic identities at lower categorical levels. This study evaluated the mineralogical characteristics of pedogenic Fe oxides in B horizons (Bw) of Fe-rich Oxisols developed from several mafic rocks in the state of Minas Gerais, Brazil. The Bw horizons were sampled at a 0.8-1.0 m depth in 13 Ferric and Perferric Rhodic Oxisols along with a Mesoferric Typic Oxisol originating from basalt, gabbro, tuffite, amphibolite and itabirite in Minas Gerais. The selected soils have taxonomic identities up to the fourth categorical level of the Brazilian System of Soil Classification. In the laboratory, the following analyses were made: a) powder X ray diffraction (XRD) of the clay fraction before and after selective concentration of Fe oxides by silicate alkaline dissolution (5 mol L-1 NaOH); b) selective chemical dissolution of the clay fraction by citrate-bicarbonate-dithionite (CBD), acid ammonium oxalate (AAO), and sulfuric acid (H2SO4 1.8 mol L-1); c) quantitative estimation of minerals in the clay fraction through allocation of phases from the XRD patterns, magnetic susceptibility of the clay fraction, and quantification of elements after sulfuric acid digestion (H2SO4 1:1) of the air-dried fine earth and treatment of the clay fraction with CBD; and d) estimation of the mean crystal size (MCS), specific surface area (SSA), and isomorphic Al-substitution (IS) of hematite, goethite, and maghemite from the XRD patterns obtained from concentrates of Fe oxides. The results showed that estimation of Fe content of maghemite by selective dissolution with 1.8 mol L-1 H2SO4 may not be accurate enough to realistically reflect the maghemite contents in the soil sample. The Al content extracted may also be influenced by other minerals that are sources of this element. Hematite crystals were predominantly placoid in shape in all Rhodic Oxisols and had smaller SSA compared to goethite, which showed both isodimensional and asymmetric habit. Higher crystallinity of maghemite and the IS values generally lower than those of hematite and goethite suggest that in well-drained soils derived from mafic rocks, the IS phenomenon in maghemites seems to result from pedogenetic advancement after its formation from magnetite oxidation.

Resumo Os pigmentos de solos são uma alternativa sustentável para a produção de tintas para a construção civil. Neste trabalho foram desenvolvidos processos de produção de tintas com pigmentos de solos, com vistas à obtenção de suspensões homogêneas e estáveis e à avaliação de seu desempenho, de acordo com a ABNT NBR 15079:2011. Foram utilizados pigmentos obtidos de três solos do município de Viçosa, MG. As formulações foram definidas por meio do delineamento experimental de misturas. O desempenho das misturas foi avaliado de acordo com os limites dos requisitos de desempenho estabelecidos pela ABNT e a viscosidade e o pH foram medidos e relacionados ao desempenho. Os resultados indicam que em nenhuma das séries foram obtidas formulações que atendessem a todos os requisitos de desempenho simultaneamente. O pH exerceu forte influência sobre o desempenho, tendo determinado a viscosidade, a resistência à abrasão e os poderes de cobertura seca/úmida. A dispersão mecânica, o "PVOH" e a morfologia das partículas dos pigmentos determinaram os resultados obtidos por este trabalho, configurando-se como temas-chave a serem abordados por outros estudos.

Abstract The soil pigments are a sustainable alternative for the production of a paint to use on buildings. In this study production processes for soil pigment based paints were developed, aimed at obtaining a homogeneous and stable suspension, as well as evaluating the paints performance according to the norms established by ABNT NBR 15079:2011. Three samples of soil pigments extracted in the city of Viçosa, MG, were used. The formulations were defined using the statistic experimental mixture design. The performance of the mixtures was evaluated according to the limits of performance requirements established by ABNT. Both viscosity and the pH were measured and related to the performance. The results indicated that none of the formulations met all the performance requirements simultaneously. The pH had strong influence on performance, having defined viscosity, abrasion resistance, and the dry/wet paint hiding power. The mechanical dispersion, the "PVOH" resin and the pigments morphology determined the results obtained in this study, having become key themes to be addressed by other projects.

As informações referentes às taxas de recuperação do boro pelo extrator em razão das doses adicionadas são escassas e necessárias para os sistemas de recomendação de adubação e corretivos. Esta pesquisa teve o objetivo de determinar as taxas de recuperação desse nutriente com água fervente e CaCl2 fervente em solos dos Estados da Bahia e Minas Gerais, na ausência e na presença de calagem. O experimento foi instalado em casa de vegetação, utilizando tratamentos em esquema fatorial (6 × 2 + 9) × 6, correspondendo a seis solos com e sem calagem, nove solos sem calagem e seis doses de B. Utilizaram-se blocos casualizados, com três repetições. As unidades experimentais foram constituídas por 0,6 dm3 de solo. A calagem foi calculada com base na análise de solo, seguindo a recomendação de calagem usada para o Estado de Minas Gerais. Após 15 dias de incubação, os solos receberam doses de B (0,0; 1,5; 3,0; 6,0; 9,0; e 15 mg dm-3), fazendo-se uma nova incubação por um período de 45 dias. Usou-se ácido bórico como fonte de B. Terminada a incubação, o teor de B disponível foi extraído com água fervente e CaCl2 5 mmol L-1 fervente, sendo a dosagem feita com azometina-H. Foram feitas análises de regressão e correlação para as diversas variáveis. O B extraído do solo com água fervente e o CaCl2 fervente, independentemente da calagem, aumentou linearmente com a elevação das doses aplicadas desse nutriente aos solos. Os extratores água fervente e o CaCl2fervente não são sensíveis à calagem. As taxas de recuperação de B dos solos pelos extratores usados variam de acordo com os teores de matéria orgânica, a quantidade e qualidade de argila e pelo equivalente de umidade. Os extratores utilizados foram altamente correlacionados entre si na extração do B do solo.

Information on rates of nutrient recovery by extractants as a function of added doses of the nutrients is scarce, yet necessary for fertilization and liming recommendation systems. The aim of this study was to determine boron recovery rates by boiling water and boiling CaCl2, with and without liming, in soils of the States of Bahia and Minas Gerais, Brazil. We set up three experiments under greenhouse conditions using a (6 × 2 + 9) × 6 factorial arrangement, consisting of six soils with and without liming, nine soils without liming, and six application rates of B. A randomized block design was used, with three replicates. Experimental units consisted of 0.6 dm3 of soil. We calculated the liming rate based on soil analysis, following the recommendation for the State of Minas Gerais. After 15 days of incubation, the soils received different application rates of B (0, 1.5, 3, 6, 9, and 15 mg dm-3); they then underwent an additional 45-day incubation period. Boric acid (H3BO3) was the B source. After incubation, available B contents were extracted by boiling water and boiling 5 mmol L-1CaCl2. Azomethine-H reagent was used for B detection. Regression and correlation analyses for the variables were carried out. The B extracted from the soil by boiling water and boiling CaCl2, regardless of liming, increases in a linear manner with the increase in the application rates of this nutrient in the soils. The boiling water and boiling CaCl2extractants proved not to be sensitive to liming. Rather, the rates of B recovered from the soils by the extractants used vary according to organic matter content, clay quantity and quality, and the moisture equivalent. The extractants used had high correlation in extraction of B from the soil.

O conhecimento etnopedológico tem fornecido informações importantes sobre o modo de vida das populações rurais a respeito de suas tradições ancestrais, como a arte de elaborar peças artesanais a partir do barro advindo de solos com características próprias a esse uso. O objetivo deste trabalho foi avaliar física, química e mineralogicamente Planossolos e Gleissolos explorados para a produção de artefatos de cerâmica artesanal em Minas Gerais. Nos barreiros, foram coletados dois perfis de Planossolos (P1 e P2) e um Gleissolo (P3) usados como matéria-prima na produção artesanal de cerâmica. Foram realizadas análises físicas e químicas, limites de liquidez (LL) e plasticidade (LP), índice de plasticidade (IP) e de atividade coloidal (IA), além da mineralogia da fração argila. Os horizontes selecionados pelos ceramistas para a fabricação de cerâmica artesanal (BA, Btg e BCg, do P1; Btg1 e Btg2, do P2; e C2g e C3g, do P3) apresentaram os maiores teores de argila e silte, IP e IA, importantes para a qualidade final da cerâmica. O horizonte Cg do perfil P1 possui potencial de ser utilizado para a produção artesanal, em virtude do seu IP, superior aos dos horizontes normalmente usados, além dos teores de argila, silte e areia fina e suas características mineralógicas. A proporção ideal das frações areia, silte e argila e a porcentagem de matéria orgânica na definição de um bom material para cerâmica são difíceis de estabelecer e variam principalmente em razão de aspectos quantitativos e qualitativos da argila nos solos.

Ethnopedological knowledge has provided important information about the way of life of rural people and their traditions, like the craft of making pieces of pottery from suitable soils. The objective of this study was to evaluate the physical, chemical, and mineralogical properties of Planosols and Gleysols used in the production of handcrafted pottery artifacts in the State of Minas Gerais, Brazil. In the clay pits, two profiles of Planosol soil (P1 and P2) and one of Gleysol soil (P3) used as raw material in the production of handcrafted pottery were collected. Physical and chemical properties, liquidity limits (LL), plasticity limits (LP), plasticity index (PI), and colloidal activity (IA) were analyzed, as well as clay mineralogy. The horizons selected by potters to manufacture handcrafted pottery (BA, Btg, and BCg for P1; Btg1 and Btg2 for P2; and C2g and C3g for P3) showed higher clay and silt, IP, and IA contents, important for the final quality of the pottery. The Cg horizon of the P1 profile has potential for craft production due to its IP, which is greater than the horizons normally used, as well as its clay, silt, and fine sand contents, and mineralogical characteristics. The ideal proportion of sand, silt, and clay and the percentage of organic matter are difficult to establish in defining good material for pottery; they vary mainly as a result of the type and proportion of clay found in the soils.

Localizado na porção centro-oeste do Estado de Minas Gerais, o Quadrilátero Ferrífero abrange uma área de aproximadamente 7.000 km². Desde o século XVII, a região é conhecida como uma província aurífera e ferrífera, sendo por essa razão uma das regiões mais bem estudadas do Brasil no contexto geológico. A região é de topografia muito acidentada, onde predominam solos pouco evoluídos pedogeneticamente, com destaque para Cambissolos Háplicos, Neossolos Litólicos e Neossolos Regolíticos. Em menor proporção e em rampas de colúvio (relevo suave ondulado), ocorrem Latossolos Vermelhos muito ricos em Fe, anteriormente denominados Latossolos Ferríferos. Neste trabalho, foram realizados estudos para caracterizar física, química e mineralogicamente amostras de nove perfis de Latossolos Vermelhos férricos e perférricos, desenvolvidos de itabirito e rochas afins no Quadrilátero Ferrífero, com os objetivos de melhor entender sua gênese e avaliar critérios taxonômicos que permitam sua diferenciação no SiBCS, em níveis categóricos mais baixos. Os elevados valores de densidade de partículas são peculiares nesses solos e, ao lado da estrutura forte, muito pequena e granular, são fatores que contribuem para subestimar os teores de argila e superestimar os de silte, resultando em relação silte/argila maior do que aquela proposta pelo SiBCS para os Latossolos. A variação dos teores de SiO2, Fe2O3, Al2O3, TiO2, MnO, P2O5 e de alguns elementos-traço aponta para a diversidade na composição química do itabirito ou, ainda, provável mistura com rochas filíticas da região. Os valores das relações Fe2O3/TiO2 (não molecular) e TiO2/Fe2O3 (molecular) revelaram-se diferentes daqueles sugeridos na literatura para separação de Latossolos Vermelhos desenvolvidos de itabirito daqueles de rochas máficas. As frações areia, silte e argila apresentaram grande variação na atração magnética, com as duas primeiras frações evidenciando maior magnetização, em razão da presença de magnetita. Os valores de substituição isomórfica de Fe por Al variaram 0,07 a 0,11 e 0,09 a 0,38 mol mol-1 nas estruturas da hematita e magnetita, respectivamente.

Located in the Midwest of the State of Minas Gerais, a region called Quadrilátero Ferrífero covers an area of approximately 7,000 km². Since the seventeenth century, it is known as gold- and iron-producing province, and the geological context is therefore one of the best-studied of Brazil. The regional topography is very rugged, with mostly poorly developed pedogenesis, especially Cambissolos Háplicos, Neossolos Litólicos and Neossolos Regolíticos. In a smaller proportion and on colluvial ramps (hilly relief), very Fe-rich Latossolos Vermelhos occur, formerly Latossolos Ferríferos. This study characterized the physical, chemical and mineralogical properties of samples from nine ferric and hyperferric Latossolo Vermelho profiles, developed from itabirite and related rocks in the Quadrilátero Ferrífero, with the objectives of improving the understanding of their genesis and establish taxonomic criteria for their differentiation in the SiBCS at lower categorical levels. The high particle density values in these soils are peculiar and along with the strong, very small and granular structure, are factors that contribute to underestimate clay and overestimate silt, resulting in a higher silt/clay ratio than proposed by SiBCS for Latossolos. Variations in the levels of SiO2, Fe2O3, Al2O3, TiO2, MnO, P2O5, and of some trace elements indicate the diversity in the chemical composition of itabirite or a probable mixture with phyllitic rocks of the region. The ratios of Fe2O3/TiO2 (non-molecular) and TiO2/Fe2O3 (molecular) reported in the literature for separation of Latossolos Vermelhos differed between soils developed from itabirite and from mafic rocks. The magnetic attraction in sand, silt and clay varied greatly; due to the presence of magnetite, magnetization was higher in the former two fractions. The values of isomorphic Al-for-Fe substitution ranged from 0.07 to 0.11 and from 0.09 to 0.38 mol mol-1 in the structures of hematite and magnetite, respectively.

The objective of this research was to determine the concentration of heavy metals in the blood (Pb, Ni and Cd), serum (Cu and Zn) and hair (Pb, Ni, Cd, Cu and Zn) of horses raised in non-industrial and industrial areas (with steel mill), and to verify the possibility to use these data as indicators of environmental pollution. The samples were collected during summer and winter, aiming to verify animal contamination related to environment and season of the year. Copper and Zn contents determined in the serum and Cd and Ni contents obtained in the blood indicated no contamination effects of industries. For some animals, contents of Pb in the blood were higher than those considered acceptable for the species, but without relationship with industrialization and without clinical signs of Pb intoxication. The heavy metals evaluated on the hair of horses in this study were not increased with the presence of industries, but Cu and Cd contents were influenced by the season. The contents of some heavy metals in biological components analyzed were influenced by season sampling; however, serum, blood and hair may not be suitable to indicate differences in environmental contamination between the two contrasting areas. Most part of the heavy metal contents was lower or close to the reference values for horses. Serum, blood and hair components from horses may not be effective as indicators of environmental pollution with heavy metals. Industrialization and seasons have no effects on most part of heavy metals contents from those components.

Identificando a rutura no desenvolvimento da ciência entre o contexto de descoberta e o contexto de justificação, julgamos poder entender melhor a dominação do ensino transmissivo da ciência em contexto escolar e melhor argumentar para a sua superação. Por outro lado, o argumento que aqui defendemos para recuperar, para o contexto de sala de aula, a fortíssima chama cultural que a ciência transporta nos seus conceitos, leis e teorias, bem como no seu próprio processo de desenvolvimento, tem uma tradição enraizada na cultura portuguesa que exploramos.

By identifying the rupture in the development of science between the context of discovery and the context of justification, we believe can better understand the domination of transmissive teaching of science in schools and argue for overcoming it. The argument is to recover for the classroom the very strong cultural flame that science carries in its concepts, laws and theories as well as in its own developmental processes. We explore the tradition rooted in Portuguese culture.

In this work, hydrotalcite, a layered double hydroxide, had its ion exchange properties combined with the magnetic properties of iron oxide to produce a magnetic adsorbent, HT-Fe 500. These magnetic composites can be used as adsorbents for anionic contaminants in water and subsequently removed from the medium by a simple magnetic process. Removal of chromium (VI) from aqueous solutions using HT-Fe 500 was achieved using batch adsorption experiments. The adsorption capacity, calculated with the Langmuir-Freundlich model showed to be dependent on temperature, reaching values of 25.93 and 48.31 mg g-1, respectively, for temperatures of 25 and 30 ºC.