Abstract The Private Reserve of Natural Patrimony (RPPN) of the Santuário of Caraça is found in a mountain region within the Quadrilátero Ferrífero geological province in the State of Minas Gerais. In this region, intense metamorphic processes shaped their siliciclastic rocks, enabling the formation of fractures and diaclasis, the favourite routes of weathering during the development of karst landscapes. The natural cavities thus formed, mainly in the RPPN sector called “Pico do Inficionado”, provide shelter for countless swifts of the species Streptoprocne zonaris and S. biscutata, responsible for the accumulation of guano on the floor. However, guano is a substance rich in nutrients, mainly phosphates and nitrates, and this is the main nutrient supply in permanently dry caves. This work studied the physical (density) and chemical (organic carbon, nitrogen, potassium, phosphorus, sodium, calcium, magnesium, aluminium and pH) characteristics of 21 guanos layers, correlating their contents with the depth of seven deposits and separating the results into factors. Considering that, knowing that the guano deposits contain crucial elements such as Ca, Mg, and especially P and N, which act as an energy source for many chemotrophic organisms, the subdivision of the studied elements allowed us to defer three factors: the first one features the concentrations of Al, P, K, Na and CO, the second one was determined for N, pH and density. Finally, the third factor was based on Ca and Mg. The quartzitic material influences the chemical and physical composition of the deepest guano. As the rock changes, elements like Al and K are released and enrich the deeper layers, as well as increasing density due to the presence of sand in the material. (RPPN Gerais rocks diaclasis landscapes formed Pico Inficionado, Inficionado , Inficionado” S biscutata floor However nutrients nitrates caves (density organic carbon nitrogen potassium phosphorus sodium calcium magnesium 2 layers factors Mg N organisms CO Finally changes

Resumo Sambaquis são sítios arqueológicos presentes principalmente próximos a costa e a sistemas flúvio-lacustres. São encontrados na maior parte do litoral brasileiro. Coletas e análises de amostras de solos e de espécies de malacofauna fornecem informações importantes sobre a ocupação humana em determinado local. Essa pesquisa teve como objetivo verificar, através da análise de elementos químicos presentes em amostras de solos, a ocorrência de ocupação humana em três sambaquis localizados no município de Guarapari, Espírito Santo, Brasil. Foram delimitados três perfis, um para cada sambaqui, denominados Una I, Una II e Concha D’Ostra. As amostras de solos foram secas, destorroadas e peneiradas. A seguir foram enviadas para análises em laboratório. Foram encontradas quantidades significativas de elementos químicos tais como fósforo, potássio, sódio, cálcio, magnésio, manganês, zinco, cobre e também de matéria orgânica. Foi verificada ainda significativa variação nos níveis de pH, na capacidade de troca de cátions, na soma de bases e saturação de bases. Os restos de espécies de malacofauna, utilizadas como fonte de alimentação pelos sambaquieiros, bem como as análises químicas das amostras de solos realizadas permitem concluir que houve ocupação humana nos três sambaquis. Altos teores de fósforo e potássio encontrados bem como o porte do sambaqui Concha D’Ostra sugerem que ali houve ocupação humana por período de tempo maior quando comparado com os sambaquis Una I e Una II.

Abstract Sambaquis are archaeological sites present mainly in coast and close to the fluvio-lake systems. They are found in most of the Brazilian coast. Sampling and analysis of soils and malacofauna species provide important information about human occupation in a given place. This research aimed to verify, through the analysis of chemical elements present in soils, the occurrence of human occupation in three sambaquis located in the Guarapari, Espírito Santo State, Brazil. Three profiles were delimited, one for each sambaqui, called Una I, Una II and Concha D’Ostra. The soil samples were dried,grinded, sieved, and then sent to the laboratory analysis. Significant amounts of chemical elements such as phosphorus, potassium, sodium, calcium, magnesium, manganese, zinc, copper and also organic matter were found. It was also verified significant change in the pH levels, cation exchange capacity, sum of bases and base saturation. The remains of malacofauna species used as food source by the sambaquieiros as well as the soil chemical analysis allow to conclude that there was human occupation in the three sambaquis. The high levels of phosphorus and potassium found in the Concha D’Ostra sambaqui as well as its scale suggest that there was human occupation there for a longer period of time than in the Una I and Una II sambaquis.

Abstract Fire behavior prediction models can assist environmental agencies with fire prevention and control. This study aimed to adjust a fire prediction model for the state of Minas Gerais, Brazil. Using the R program and hotspots provided by the National Institute for Space Research (INPE) for 2010, prediction of the probability of fires through the Random Forest algorithm was conducted using the Bootstrapping method. The model generated a prediction map with global kappa value of 0.65. External validation was performed with hotspots in 2015. Results showed that 58% of the hotspots are in areas with ignition probability > 50%, being 24% of them in areas with 25-50% probability, and 17% in areas with < 25% probability. These results were considered satisfactory, demonstrating that the model is suitable for predicting fires.

ABSTRACT The term Post-Barreiras is a definition for sediments above the deposits of the Barreiras Formation, and the genesis of soils in these environments must be related to sedimentary deposition. Our objective was to apply multi-technique analyses to characterize the sediments and soils to understand pedogenesis in these environments. We analysed sedimentological parameters and the geochronology of sediments. Morphological, chemical, and mineralogical analyses allowed the characterization of the soil. Also, these data supported the analysis of lithological discontinuity. We considered the contents of Ti and Zr, uniformity value, the fraction of organic material, morphology, and palynological analysis. The age of Post-Barreiras sediments is from the Pleistocene, and they have a more significant variation of sedimentological parameters concerning Barreiras Formation layers. In general, the soils are sandy, acidic, have a low level of exchangeable cations. Mineralogy has a predominance of quartz and kaolinite minerals. In the region, there are soils with low morphological variation, classified as Quartzipsamments. In other cases, there are soils with apparent spodic morphology, which is conditioned by four aspects: (i) Podzolization in Post-Barreiras sandy sediments without evidence of lithological discontinuity, forming Bs horizon (Spodosols); (ii) contact zones (Post-Barreiras/Barreiras Formation) with physical, chemical, and morphological evidence of discontinuity, forming Quartzipsamments or Ultisols; (iii) layers of the Barreiras Formation buried by Post-Barreiras sediments and the subsequent podzolization process, forming Bhm horizon (Spodosols); and (iv) destruction of Ultisols clay, forming Bs horizon (Spodosols). The sedimentary association (Post-Barreiras/Barreiras Formation) favors the development of different soils. The contact zones generate a morphological aspect similar to the Spodosols, associated or not with podzolization processes.

RESUMO A correção da acidez é fundamental para a atividade agrícola em solos ácidos, assim como a caracterização e estudo do efeito no solo de fontes alternativas de corretivos. Objetivou-se caracterizar os calcários de origem biológica, sedimentar e metamórfica. Os calcários estudados foram: biogênico (CB), sedimentar (CS), comercial (CC) e o mármore (CM). Foram avaliados: poder relativo de neutralização total (PRNT); composição química; área superficial específica e liberação de Ca2+ e Mg2+ nas concentrações de 0,10; 0,50; 1,00 e 2,00 mol L-1 de HCl e os efeitos no solo, após 90 dias da aplicação dos calcários. O Si identificado contribuiu para o menor PRNT do CB (73,7%) e CC (74,4%). Nas menores concentrações de HCl, o CB mostrou-se mais reativo, porém com o aumento da concentração do HCl, o CM passou a ser mais reativo. Os maiores teores de CaO (58,32%) e MgO (13,05%) foram observados no CS e CM, respectivamente, que contribuíram com maiores aportes de Ca2+ (3,95 cmolc dm-3) e Mg2+ (1,09 cmolc dm-3), quando aplicados ao solo. Todos os calcários promoveram elevação do pH e redução do H+Al no solo. Os teores de Ca2+ e Mg2+ no solo foram influenciados pela composição dos corretivos.

ABSTRACT Liming acid soils is fundamental for agricultural activity such as the study and characterization of alternative liming material. The objective of this study was to characterize biological, sedimentary, and metamorphic limestones. The following limestones were studied: biogenic (BL), sedimentary (SL), commercial (CL), and marble (ML). This study evaluated total relative neutralizing power (TRNP), chemical composition, specific surface area, and Ca2+and Mg2+release at concentrations of 0.10, 0.50, 1.00, and 2.00 mol L-1 HCl, in addition to the effects on the soil 90 days after limestone application. The Si identified contributed to the lower TRNP of BL (73.7%) and CL (74.4%). At the lowest HCl concentrations, BL was the most reactive, but with an increase in concentration, ML became the most reactive. The highest CaO (58.32%) and MgO (13.05%) levels were observed in SL and ML, respectively, which contained the highest Ca2+(3.95 cmolcdm-3) and Mg2+ (1.09 cmolcdm-3) concentrations when applied to the soil. All the limestones increased pH and lowered soil H+Al. Soil Ca2+and Mg2+were influenced by the composition of the amendments.

ABSTRACT The objective of this study was to map the levels of degradation of pastures and its association with chemical properties of the soil and relief. We selected a sub-basin located in the municipality of Viçosa, Minas Gerais, and we mapped the degradations through Ikonos images that were submitted for classification. Soil samples were collected and analyzed chemically; the results were transformed in spatial data using cokriging, based on variables of the digital elevation model. We associated the maps (cokriging) with data from exposure of the hillside, levels of solar radiation and levels of the pastures’ degradation. The pastures were mainly classified in moderate (44%) and very strong (30%) degradation levels. The areas with mild degradation tend to increase when there is a higher sum of bases, cationic exchange capacity and organic matter. The portions facing North and the increase of solar radiation showed more advanced stages of degradation.

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.

The objective of this work was to synthesize and characterize Layered Double Hydroxides (MgAl-LDHs, MgFe-LDHs, and MgAlFe-LDHs) containing phosphate anions and study P release kinetics was conducted with the prepared materials. The release kinetics tests were performed in water by the stirred-flow method to verify the P release profile from LDHs materials. Results showed LDHs have similar characteristics to those of reactive sources of P, such as thermophosphates. The LDHs presented gradual P release and the LDH prepared with the molar ratio of cations Mg:Al = 2:1 showed a more sustained profile of P release compared to other produced materials. Thus, the chemical and structural characteristics of the LDHs make them potential materials for the use and storage of slow P release fertilizer.

RESUMO O biocarvão, produto da pirólise de resíduos orgânicos, vem sendo utilizado como condicionador de solo e como alternativa na gestão de resíduos sólidos. O objetivo deste trabalho foi avaliar o efeito da temperatura de pirólise nas propriedades químicas, físicas, mineralógicas e a extração ácida de metais em biocarvões produzidos a partir de resíduos de bagaço da cana-de-açúcar, eucalipto e lodo de esgoto. Foram avaliados os teores de C, H, N, O; cinzas; macro e micronutrientes, além de alguns contaminantes; relações molares O/C e H/C; difratometria de raios X; grupos funcionais por FTIR. Além disso, foi determinada a liberação de nutrientes e contaminantes pela extração em concentrações crescentes de HNO3 (0,01-2,0 mol L-1). As relações O/C e H/C diminuíram com o aumento da temperatura de pirólise, o que caracteriza uma maior estabilidade do C dos biocarvões. O biocarvão de lodo de esgoto (BC-L) apresentou as maiores taxas de liberação de nutrientes e metais contaminantes (Cd, Cr, Ni e Pb). A extração ácida dos demais biocarvões foi muito baixa (< 20% do teor total). Os resultados indicam que a fração carbonosa do biocarvão contribui para a baixa taxa de liberação dos elementos em meio ácido.

ABSTRACT The biochar, product of pyrolysis of organic waste, has been used as a soil conditioner and alternative on solid waste management. However, the raw material and pyrolysis temperature used influence the quantity and dynamics of release of nutrients and contaminants from the biochar. The objective was to evaluate the use of waste sugarcane bagasse, eucalyptus and sewage sludge for production of biochar and determine the chemical, physical, mineralogical properties and acid extraction of these materials produced at 350 °C and 500 °C. Were evaluated the proportion of C, H, N, O; ashes; macro and micronutrients, plus some contaminants; characterization of mineral phases by diffractometry of X- rays; functional groups by infrared absorption spectroscopy (FTIR). Moreover, it was determined the release of nutrients and contaminants for the extraction in increasing concentration of HNO3 (0,01 - 2,0 mol L-1). The O/C and H/C relations decreased with increasing temperature of pyrolysis, which define a greater stability of the C of biochars. Sewage sludge biochar (BC-L) had the highest nutrient release rates and contaminant metals (Cd, Cr, Ni and Pb). Acid extraction of other biochars was very low (<20% of the total content). The results indicate that the carbon fraction of biochar contributes to the low rate of release of the elements in acid place.

RESUMO No presente artigo, aborda-se a técnica de estabilização dos solos para uso em estradas florestais, com a análise da influência da cal hidratada na estruturação da fração areia de um solo artificial composto pelas frações areia de dois solos naturais, de modo a simular um processo natural de formação de camadas arenosas no campo, empregando-se sistemas binários de empacotamento de partículas. A pesquisa abrangeu os seguintes tópicos: (i) caracterização da resistência mecânica e da condutividade hidráulica dos sistemas binários do solo artificial; e(ii) estudo da influência da cal hidratada na estruturação dos sistemas de empacotamentos binários do solo artificial. As amostras de solo foram submetidas a pré-tratamentos para obtenção da fração areia limpa e posterior peneiramento para separação em vinte e uma classes, entre os diâmetros de 0,053 e 2,000 mm, e trabalhando-se com relações entre o diâmetro maior (D) e o diâmetro menor (d) na faixa de 5,7 a 13,4. Sequencialmente, foram preparados corpos de prova de empacotamentos binários do solo artificial e deste com a adição de 2% de uma cal hidratada comercial. Posteriormente, os corpos de prova foram submetidos aos ensaios de laboratório de permeabilidade, para determinação da condutividade hidráulica, e de resistência à penetração empregando-se um cone penetrométrico quase-estático, para determinação da resistência de ponta. Com base nos resultados obtidos, concluiu-se que: (i) a condutividade hidráulica e a resistência à penetração dos empacotamentos binários do solo artificial apresentaram reduções à medida que se aumentou a relação D/d; e (ii) a cimentação por cal hidratada reduziu a permeabilidade e elevou a resistência à penetração dos empacotamentos binários do solo artificial.

ABSTRACT This paper addresses the topic soil stabilization for forest roads applications and analyzes the influence of the hydrated lime in structuring the sand fraction of an artificial soil composed of the sand fractions of two natural soils, simulating natural process of cementation of sands and using binary packing systems. The study included the following topics: (i) characterization of the mechanical strength and hydraulic conductivity of binary systems of the artificial soil; and (ii) effect of hydrated lime in structuring binary packing systems of the artificial soil. Soil samples were submitted to chemical pre-treatment, to obtain clean sand fractions from the two sandy soils with particle diameters ranging from 0.053 to 2 mm, following sieving and separation of them in twenty-two classes with maximum (D)/minimum (d) ratios varying from 5.7 to 13.4. Sequentially, binary packing specimens of the artificial soil were prepared and then stabilized with 2% of a commercial hydrated lime. Next, the specimens were submitted to permeability and quasi-static cone penetration tests, in order to determine their hydraulic conductivity and cone tip resistance. Based on the obtained results, it was concluded that: (i) in the artificial soil, an increase of D/d ratio led to an increase of cone tip resistance and decrease of hydraulic conductivity; and (ii) cementation with hydrated lime reduced the hydraulic conductivity and increased the cone tip resistance.

RESUMO Estudos de morfologia assumem importância expressiva na análise de fenômenos de empacotamento em sistemas granulares, em especial com vistas ao emprego da técnica de estabilização de solos denominada correção granulométrica em estradas florestais. Neste contexto, o presente artigo teve como objetivo desenvolver e tornar operacional um Sistema para a Captura de Imagens de Grãos de Areia e, por meio deste, determinar os índices morfológicos da fração areia de dois solos arenosos denominados João Pinheiro (JP) e Cachoeira da Prata (CP). As amostras dos solos, após secagem ao ar, foram passadas na peneira de abertura nominal 2,0 mm, para a retirada da fração pedregulho. Os materiais que passaram na peneira de 2,0 mm foram submetidos à dispersão, lavagem na peneira de abertura nominal 0,053 mm, remoção de matéria orgânica e de óxidos de ferro, para obtenção das frações areia limpa dos solos. Posteriormente, cada amostra de solo foi submetida a peneiramento, para separação em doze classes, entre os diâmetros de 0,149 mm e 1,190 mm, utilizando-se um agitador tipo Rotap. Na sequencia, foram realizados ensaios de caracterização dos atributos morfométricos das doze classes das frações areias dos solos. Para fins de validação dos resultados obtidos com o Sistema de Captura de Imagem de Grãos de Areia, adotou-se como base o conjunto de resultados de parâmetros morfométricos determinados previamente com um sistema tradicional de análise de imagens. A análise dos resultados possibilitou concluir que: (i) a fração areia do solo JP apresentou valores superiores para os índices morfométricos arredondamento, compacidade e alongamento em comparação com a fração areia do solo CP; e (ii) o Sistema de Captura de Imagem de Grãos de Areia funcionou de forma adequada, com praticidade.

ABSTRACT Morphology studies assume significant importance in analysis of phenomena of granular systems packaging, in particular with a view to the use of the technique of soil stabilization named particle size correction in forest roads. In this context, this study aimed to develop and operationalize a Sand Grain Image Capture System and, hereby, determine the morphological indices of the sand fractions of two sandy soils called João Pinheiro (JP) and Cachoeira da Prata (CP). Soil samples, air-dried, were sieved (2.0 mm nominal mesh size) for removal of gravels. The materials that passed through the sieve were subjected to dispersion, washing in 0.053 mm nominal mesh size sieve, removal of organic matter and iron oxides to obtain the clean sand fractions. Subsequently, each soil sample was sieved for separation into twelve classes, between the diameters of 0.149 mm and 1.190 mm, using a Rotap shaker. Next, tests were carried out to characterize the morphometric attributes of the twelve classes of sand fractions of the soils studied. For validation of the performance of the Sand Grain Image Capture System, the results were compared to those obtained using a standard procedure for image analysis. The analysis of the results led to the following conclusions: (i) the sand fraction of the JP soil presented higher values for the morphometric indices roundness, elongation and compactness compared to sand fraction of the CP soil; and (ii) the Sand Grain Image Capture System worked properly, with practicality.

Resumo Embora haja alguns trabalhos a partir da década de 80, pouco se sabe sobre a origem e mecanismos de depósitos destes sedimentos. O objetivo deste estudo foi analisar os parâmetros sedimentológicos, morfologia granulométrica e datação dos sedimentos. Foram coletadas amostras de Pós-Barreiras e sedimentos de praia, na qual foram submetidas a dispersão da argila e silte, com uso de NaOH 0,1 mol L-1; a fração areia foi separada em intervalos de 1/2 phi [Φ]. Foi analisado a morfologia dos grãos via microscópio ótico. Empregou-se a datação em amostras pelo método de Luminescência Opticamente Estimulada. Os resultados indicam que os sedimentos Pós-Barreiras foram depositados em ambiente de elevada energia, presumivelmente pela contribuição maior de processos marinhos com possíveis retrabalhamentos eólicos. Os sedimentos de praia frontal apresentaram características de deposição eólica. As datações definiram que a deposição dos sedimentos Pós-Barreiras foi do Pleistoceno tardio até o Holoceno (de 6.9 a 85.4 ap). A posição altitudinal dos sedimentos Pós-Barreiras (40 a 150 m), não pode ser associada a qualquer nível de elevação mar conhecida, o que surge a hipótese de processos de neotectônicos promovendo a elevação.

Abstract Although there is some work from the 80s, little is known about the origin and mechanisms of these sediment deposits Post-Barreiras. The aim of this work was to analyze the sedimentological parameters, particle size and morphology of grains of sand and dating of sedments. samples Post-Barreiras and beach sediments were collected, which were subjected to dispersion of clay and silt, using NaOH 0,1 mol L-1; the sand fraction was separated at intervals of 1/2 phi [Φ]. The morphology of the grain was analyzed through optical microscope. We used the dating of three samples by the method of Optically Stimulated Luminescence. Results indicate that the Post-Barreiras sediments they were deposited at high energy environment, presumably by a higher contribution of marine processes with possible aeolian reworkings. Beach front sediments showed characteristics of aeolian deposition. The dates determined that the deposition of Post-Barreiras sediments was from the late Pleistocene to Holocene epoch (from 6,950 to 85,350ka). The altitudinal position of Post-Barreiras sediments (40-150m) cannot be associated to any known sea elevation level, which then emerges the hypothesis of neotectonic processes promoting elevation.

Resumen Aunque hay algunas obras de los años 80, poco se sabe sobre el origen y los mecanismos de los depósitos de sedimentos la formación Barreiras. El objetivo del presente trabajo fue analizar los parámetros sedimentológico, morfología de los granos y la datación de sedimentos. Se recogieron muestras de sedimentos Pós-Barreiras y sedimentos de la playa, en el que se sometieron a la dispersión de arcilla y limo, utilizando NaOH 0,1 mol L-1; la fracción de arena se separó a intervalos de 1/2 phi [Φ] y la morfología del grano se analizó por medio de microscopio óptico. Utilizó la datación de muestras por el método de luminiscencia ópticamente estimulada. Los resultados indican que los sedimentos Pós-Barreiras fueron depositados en ambiente de alta energía, presumiblemente por el aumento de la contribución de los procesos marinos con posible reelaboración viento. Los sedimentos de la playa delanteros mostraron características eólicas. Las edades determinaron que la deposición de los sedimentos Pós-Barreiras fue a finales del Pleistoceno al Holoceno (de 6.9 a el 85,4 ka). La posición latitudinal de los sedimentos Pós-Barreiras (40 a 150 m) no se puede asociar con cualquier aumento del nivel del mar conocido, posiblemente, la que aparece que procesos neotectónicos han promovido la elevación.

RESUMO: A dinâmica da matéria orgânica influencia os principais processos químicos, físicos e biológicos nos solos e determina muitas vezes seu comportamento químico e sua fertilidade. É fundamental a quantificação das frações que compõem a matéria orgânica para a compreensão dos processos pedogenéticos que refletem ou induzem as propriedades dos solos. O objetivo do estudo foi avaliar o comportamento da matéria orgânica do solo de diferentes perfis de solos sob formações deciduais, por meio do fracionamento químico da matéria orgânica e obtenção de suas diferentes frações oxidáveis. Dez perfis de solo foram descritos e coletados em áreas de formações deciduais em municípios de Minas Gerais e Bahia. Foram realizadas análises químicas e físicas em cada horizonte. Para as frações da matéria orgânica foi realizado o desmembramento de substâncias húmicas e posterior determinação de carbono de cada fração, quais sejam, humina (C-HUM), ácido fúlvico (C-FAF) e ácido húmico (C-FAH), e calculadas suas relações e o percentual de cada fração em relação a C orgânico total (COT), %FAF, %FAH, %HUM e %EA, além das frações de C oxidável em cada horizonte avaliado. As substâncias húmicas que compõem a matéria orgânica dos solos de perfis de Florestas Estacionais Deciduais mostraram que este compartimento da MOS apresentou predomínio da fração humina, seguido dos ácidos húmicos e com menor teor de C, e os ácidos fúlvicos para a maioria dos solos. Já as diferentes frações de C oxidável puderam apontar frações mais lábeis associadas aos horizontes superficiais e mais recalcitrantes aos horizontes subsuperficiais.

ABSTRACT: The dynamics of organic matter influences the main chemical, physical and biological processes in soil, and often determines their chemical behavior and fertility. Therefore, it is essential to quantify the fractions that make up the organic matter to the understanding of pedogenic processes that reflect or induce soil properties. The aim of the study was to evaluate the behavior of soil organic matter in different soil profiles under deciduous formations, through fractionation of organic matter and obtain their different oxidizable fractions. Ten soil profiles were described and collected in areas of deciduous formations in the state of Minas Gerais and Bahia. Chemical and physical analyzes were performed on each horizon. For organic matter fractions, the fractionation of humic substances and subsequent determination of carbon in each fraction was performed: humin (HUM - C) , fulvic acid (C - FAF) and humic acid (C - FAH) and calculated their relations and percentage of each fraction relative to total organic carbon (COT) , %FAF, %FAH, %HUM and %EA, beyond fractions oxidizable C in each evaluated horizon. Humic substances that make up the organic matter in the soil of seasonal dry forests profiles showed that this compartment MOS showed a predominance of the humin fraction, followed by humic acids and lower content of C, fulvic acids for most soils. However, the different fractions of oxidizable C could already point more labile fractions associated with surface horizons, and more recalcitrant to subsurface horizons.

O K é um nutriente encontrado em baixos teores em solos brasileiros, sendo necessário grande aporte via fertilização para alcançar produtividades satisfatórias das culturas. O Brasil apresenta elevada dependência externa e possui limitadas reservas de minerais solúveis de K, tradicionalmente explorados para a produção de fertilizantes. Por outro lado, é comum a ocorrência no país de minerais silicatados ricos em K não explorados comercialmente. Neste trabalho, objetivou-se caracterizar mineralógica e quimicamente amostras de verdete, separadas em frações granulométricas e avaliar seu potencial de uso com fertilizante potássico.A composição mineral do verdete é à base de glauconita, quartzo e feldspatos. Os teores totais de K2O no verdete variaram de 5,18 a 9,0 dag/kg. O teor de K extraído em água ou em ácido cítrico a 2% foi inferior a 2,4% do K total, indicando baixa reatividade do verdete e limitações para seu uso direto como fonte de K. O fracionamento físico e a sedimentação em água são processos ineficientes para promover a concentração de K nas diferentes frações do verdete. Os teores totais de K em algumas amostras de verdete são consideráveis, podendo viabilizar o uso desta rocha como matéria prima para produção de fertilizantes potássicos mais reativos.

Potassium is a nutrient found at low levels in Brazilian soils, requiring large inputs of fertilizers to achieve satisfactory crop yields. Brazil has high external dependence and limited reserves of soluble K mineral, which is traditionally exploited for the production of fertilizers. On the other hand, it is common the occurrence in the country of potassium-rich silicate minerals which are not commercially exploited. This study aimed to characterize mineralogically and chemically samples of verdete rock separated into size fractions and evaluate its potential as potassium fertilizer. The mineral composition of verdete rock is based on glauconite, quartz and feldspar. The total K2O content in verdete rock ranged from 5.18 to 9.0 dag/kg. The K content extracted in water or 2% citric acid was 2.4% below the total of K, indicating low reactivity of verdete rock and limitations for direct use as K source. The processes of physical fractionation and sedimentation in water are inefficient to promote the concentration of K in the different verdete rock fractions. The total K content in some samples are considerable and may enable the use of this rock as raw material for production of more reactive potassium fertilizers.

Este trabalho de revisão tem como objetivo apresentar os Hidróxidos Duplos Lamelares (HDL) como nanomateriais para serem aplicados na agricultura, com destaque para a utilização desses como matrizes para o armazenamento e a liberação lenta de nutrientes e agroquímicos para o cultivo de plantas. São abordadas as características estruturais, as principais propriedades e os principais métodos de síntese e de caracterização dos HDL. São também reportados trabalhos da literatura, demonstrando a potencial aplicação desses materiais no armazenamento e na liberação lenta de nitrato , fosfato, agroquímicos, além da utilização como adsorventes. Pretende-se com esta pesquisa expandir, em um futuro próximo, o campo de investigação desses materiais com aplicação na agricultura, aumentando a interface entre a química e a agronomia.

The current research aims to introduce Layered Double Hydroxides (LDH) as nanomaterials to be used in agriculture, with particular reference to its use as storage and slow release matrix of nutrients and agrochemicals for plant growing. Structural characteristics, main properties, synthesis methods and characterization of LDH were covered in this study. Moreover, some literature data have been reported to demonstrate their potential for storage and slow release of nitrate, phosphate, agrochemicals, besides as being used as adsorbent for the wastewater treatment. This research aims to expand, in near future, the investigation field on these materials, with application in agriculture, increasing the interface between chemistry and agronomy.