Resumo O cultivo de videiras em regiões com elevadas precipitações pluviométricas, como no sul do Brasil, envolve o uso de fungicidas para o controle das doenças fúngicas foliares. Estes fungicidas, normalmente, contêm em sua composição cobre (Cu) e zinco (Zn), promovendo o acúmulo desses metais no solo. O objetivo do trabalho foi avaliar a distribuição de Cu e Zn nas frações físicas granulométricas em solos de vinhedos do sul do Brasil. Foram coletadas amostras de solo (0-5 e 10-20 cm), em duas áreas de vinhedos e uma área de mata em três regiões do sul do Brasil, sendo uma no estado de Santa Catarina e duas no Rio Grande do Sul. As amostras da camada de 0-5 cm foram fracionadas em > 50 μm e < 50 μm. Nas amostras de solo e nas frações foram determinados os teores totais de Cu e Zn por fluorescência de raio-X. As áreas de vinhedos do sul do Brasil apresentam grandes variações nos teores totais de Cu e Zn, devido as distintas características dos solos e ao histórico de cultivo. Para o Cu não há distinção entre as frações, mas o Zn acumula, preferencialmente, na fração <50 μm.

Abstract The cultivation of vines in regions with high rainfall, as in southern Brazil, involves the use of fungicides to control foliar fungal diseases. These fungicides normally contain copper (Cu) and zinc (Zn) in their composition, promoting the accumulation of these metals in the soil. The objective of this work was to evaluate the distribution of Cu and Zn in the granulometric physical fractions in soils from vineyards in southern Brazil. Soil samples (0-5 and 10-20 cm) were collected in two areas of vineyards and a forest area in three regions of southern Brazil, one in Santa Catarina and two in Rio Grande do Sul states. Samples from the 0-5 cm layer were fractionated into > 50 μm and < 50 μm. In the soil samples and in the fractions, the total contents of Cu and Zn were determined by X-ray fluorescence. Vineyard areas in southern Brazil show great variations in total Cu and Zn contents, due to different soil characteristics and cultivation history. For Cu, there is no distinction between the fractions, but Zn accumulates, preferentially, in the fraction <50 μm.

Abstract Background The use of carbonaceous materials for environmental remediation is attractive due to low expense and high sorption capacity. However, their efficiency in contaminant removal is affected by substrate composition and sorption mechanism. Objective This study investigated atrazine sorption and desorption in three carbon-rich substrates. Data were evaluated considering isotherm models and sorbent chemical composition. Methods Sorption was performed by the batch equilibrium method with three substrates obtained from pig slurry composting with different proportions (w/w) of charcoal fines (CF): CF0, CF9 (9% CF), and CF18 (18% CF). The substrates were characterized by elemental analysis, 13C NMR CP/MAS spectroscopy. The Freundlich and Dubinin-Radushkevich (DRK) models better fitted the sorption data (0.96>R2>0.81), followed by Temkin (0.95>R2>0.76). Charcoal addition to composting substrates increased carbon content and the aromaticity in the order CF0<CF9< CF18. However, the sorption affinity decreased in the opposite order as indicated by the Kf values: 675, 335 and 290 L kg-1, respectively. Values of the E parameter (DRK) varied from 8.05 to 8.29 kJ mol-1, suggesting a predominant physical sorption mechanism, whereas the Bt coefficient (Temkin) indicated an endothermic process. Desorption was only observed at higher atrazine concentrations (>10 mg L-1), and the desorption Kf values were greater than the respective sorption values. Conclusions Atrazine sorption in the tested C-rich substrates is not governed by the carbon content or aromaticity. The low sorption reversibility implies a low atrazine mobility from the tested substrates and suggests their potential for herbicide removal in the environment.

The aim of this study was to investigate impacts of Amazon Forest (AF) fire and conversion to pasture on carbon accumulation in particle size fractions and organic matter (OM) composition of an Acrisol. Soil samples were collected (0.00-2.00 m depth) in three sites: native AF (NAF); AF under natural regeneration for two years after burning (BAF); 23-years old Brachiaria pasture after AF burning (BRA). Assuming NAF area as reference, BAF and BRA areas showed negative carbon balance when carbon emitted to the atmosphere at AF burning is taken into account. Soil OM aromaticity and hydrophobicity, assessed via 13C nuclear magnetic resonance, in BRA and BAF were similar to that in NAF. Fire and post-fire land use altered the carbon distribution in sand, silt and clay along the soil profile and seem to have affected organo-mineral and OM self-assemblage interactions, since the relation between total soil carbon and carbon in clay was asymptotic in BAF and linear in NAF and BRA.

In high-altitude montane forests, the vascular plants undergo mycorrhizal symbiosis with mycorrhizal fungi as a strategy to face extreme soil and climate conditions. In this study, glomalin content related to soil proteins (GRSP) was studied, an insoluble glycoprotein produced by hyphae of arbuscular mycorrhizal fungi and deposited on the soil, four years after a wildfire of variable severity, in Araucaria araucana forest in south-central Chile (38° S). For the previously stated, the aim proposed was to determine the content of this glycoprotein as well as to evaluate and relate the composition of soil organic matter to the content of this glycoprotein. Samples were collected at different depths (0-5, 5-10, 10-20 and 20-30 cm, respectively) from areas presenting various fire severities (low, medium and high) and an unburned soil area (control soil). Furthermore, composition and structure of soil organic matter was studied by Nuclear Magnetic Resonance Spectroscopy of 13C (NMR 13C). As main results, total GRSP concentration showed significant differences between the burned soil and the control soil. A significant correlation between the composition of the organic matter and GRSP was found. The high concentration of GRSP obtained in burned forests could answer to an ecological-evolutionary strategy from the Araucaria araucana forest in their adaptation to both a soil with low nutrient availability and to periodical fire catastrophic events; suggesting their key role in the recovery of these ecosystems and should be considered in restauration programs.

En bosques de alta montaña, las plantas vasculares establecen simbiosis con hongos micorrícicos como una estrategia a condiciones edafo-climáticas extremas. En este estudio, se analizó el contenido de glomalina relacionada a las proteínas del suelo (GRSP), una glicoproteína producida por hongos micorrícicos arbusculares y depositada en el suelo, después de cuatro años de ocurrido un incendio de severidad variable en un bosque de Araucaria araucana en el Centro-Sur de Chile (38°S). Para lo anterior, se propuso como objetivo determinar el contenido de esta glicoproteína en el suelo así como evaluar y relacionar la composición de la materia orgánica con el contenido de esta. Se analizó muestras de suelo a distintas profundidades (0-5, 5-10, 10-20 y 20-30 cm, respectivamente) en sectores con diversos niveles de severidad de incendio (baja, media, alta) y un área no afectada por el incendio (control). Adicionalmente, se estudió la estructura y composición de la materia orgánica mediante espectrometría de resonancia magnética nuclear del 13C (13C RMN). Como principales resultados, la concentración de GRSP mostró diferencias significativas entre el suelo quemado y suelo control. Se encontró una significativa correlación entre la composición de la materia orgánica y GRSP. La alta concentración de GRSP en los bosques quemados, podría responder a una estrategia ecológico-evolutiva de los bosques de A. araucana en su adaptación a suelos con limitantes nutricionales y sometidos a eventos catastróficos periódicos de incendios, que sugieren su rol clave en la recuperación de estos ecosistemas y deberían ser considerados en programas de restauración.

Nas três últimas décadas, o cultivo de espécies exóticas vem sendo introduzido nas áreas de pastagem de solos de altitude localizados na região nordeste do Estado do rio Grande do Sul. Essa alteração de uso do solo pode causar mudanças drásticas nos atributos do solo. Avaliou-se o impacto do florestamento com Pinus Taeda nos atributos químicos e na composição da matéria orgânica (MOS) de Neossolos Litólicos dos Campos de Cima da Serra, RS. Foram estudadas amostras de solo sob plantação de Pinus há oito (Pi8) e há 30 anos (Pi30) e sob pastagem natural (NP), sendo determinados os teores de cátions trocáveis e de micronutrientes e o pH do solo. A composição da MOS foi investigada por análise elementar e espectroscopia de FTIR. O solo sob pastagem apresentou maior teor de nutrientes e de MOS comparativamente aos solos sob Pinus, refletindo a maior taxa de decomposição de resíduos subsuperficiais em ambiente de campo. A MOS apresentou maior proporção de carboidratos e de estruturas de origem microbiana nos solos sob pastagem natural. Além da depleção de nutrientes e de MOS, florestamento com Pinus afetou a qualidade da MOS: ao longo do tempo a proporção de estruturas quimicamente recalcitrantes e de grupos carboxílicos aumentou, enquanto a de grupos nitrogenados diminuiu.

In the last three decades, exotic tree species are being introduced in the natural pastures of the highlands located at the northeastern part of Rio Grande do Sul State (RS), Brazil. This alteration of land use may impart drastic changes in the soil attributes. In this context, this work aimed to evaluate the impact of Pinus taeda afforestation on soil chemical attributes and organic matter (SOM) composition in Leptosols from Campos de Cima da Serra, RS. Soil samples under eight year old (Pi8) and 30 year old (Pi30) Pinus plantations and under native pasture (NP) were studied. Contents of exchangeable cations and of micronutrients and soil pH were determined. The SOM composition was investigated by means of elemental analyses and FTIR spectroscopy. The soil under pasture had a higher content of nutrients and of SOM in comparison to Pinus soils, reflecting the higher input and decomposition rate of the below ground added residue in the grassland environment. The SOM in pasture soils showed a higher content of carbohydrate and of structures derived from microbial metabolism. Besides the depletion of nutrients and of SOM, Pinus afforestation affected the SOM quality: following afforestation, the proportion of chemically recalcitrant structures and of carboxylic groups increased, whereas N-containing groups decreased.

A queima da pastagem após o inverno é uma prática antiga em solos de altitude, que visa principalmente ao rebrote da vegetação. Entretanto, o impacto do manejo da pastagem na matéria orgânica do solo de Neossolo de altitude ainda é pouco conhecido. O presente trabalho propôs-se a investigar a composição e o teor de matéria orgânica em perfis de Neossolo da região de São José dos Ausentes, RS, e relacionar os resultados com a ocorrência de queimadas e com o pastejo, empregando como comparação solo sob mata nativa. Os ambientes estudados foram: campo nativo pastejado (2 animais ha-1) sem queima há 22 anos, campo nativo pastejado sujeito à queima bienal (0,5 animal ha-1) e mata nativa adjacente à área de pastagem. Foram coletadas amostras compostas nas camadas de 0-5, 5-10, 10-15 e 15-30 cm, sendo determinados os teores de óxidos de Fe (Fe d e Fe o), de C e de N e realizadas análises de espectroscopia de infravermelho e de termogravimetria. O ambiente alterado periodicamente pelo fogo apresentou maior teor de matéria orgânica em camadas subsuperficiais e, em geral, maior proporção de estruturas quimicamente mais lábeis, comparativamente à pastagem sem queima. Nesse ambiente, o menor teor de C foi atribuído ao pastejo mais intensivo do que o da pastagem alterada pelo fogo. A distribuição de C no ambiente de mata nativa assemelhou-se à de pastagem sem queima. No entanto, na mata a proporção de matéria orgânica de baixo peso molecular extraível com solução de HCl 0,1 mol L-1, relacionada principalmente à atividade microbiana, superou aquela encontrada sob pastagem nativa.

Burning pastures after the winter is a traditional practice in highland soils, whose main purpose is the regrowth of vegetation. However, the impact of fire, as well as the influence of grazing on the organic matter of Leptosols is still unknown. The purpose of this study was to investigate the composition and content of organic matter in soil profiles from São José dos Ausentes, state of Rio Grande do Sul, and to relate the results with the occurrence of burning and grazing, in comparison with a soil under native forest. The following environments were studied: grazed native pasture (2 animals ha-1) without burning for 22 years; grazed native pasture (0.5 animals ha-1) burned every two years; and native forest adjacent to the pasture area. Composed soil samples were collected from four layers (0-5, 5-10, 10-15 and 15-30 cm) in which contents of C, of N, and of iron oxides (Fe d and Fe o) were determined and infrared spectroscopy and thermogravimetry analyses performed. The subsurface layers of the fire-affected environment contained greater organic matter contents, and in general, a composition with higher proportion of chemically labile structures, in comparison with the unburned pasture. In the latter environment, the lower C content than in the burned pasture was ascribed to more intensive grazing. The C distribution in the native forest environment was similar to that of the unburned pasture. Nevertheless, in the samples under forest, the proportion of organic matter of low molecular weight, extractable with 0.1 mol L-1 HCl and related mainly to microbial activity, exceeded that of the pasture environment.

Soil organic matter is the main sorptive soil compartment for atrazine in soils, followed in a minor scale by the inorganic fraction. In this study, the soil organic matter quality and atrazine sorption were investigated in four different soil types. The pedogenic environment affected the humification and therefore the chemical composition of the organic matter. The organic matter contribution to atrazine sorption was larger (60-83%) than that of the inorganic fraction. The organic matter capacity in retaining the herbicide was favoured by a higher decomposition degree and a smaller carboxylic substitution of the aliphatic chains.

A região dos Campos de Cima da Serra, RS, apresenta solos com elevados teores de matéria orgânica (MOS), sendo freqüente teores altos de Al trocável. A proposta deste trabalho foi investigar a qualidade da MOS de amostras de camadas superficiais (0 a 10 cm) de oito solos representativos da região (dois Neossolos, dois Gleissolos, três Cambissolos e um Latossolo) sob pastagem nativa, com os seguintes objetivos: avaliar seu comportamento diante da desmineralização da amostra com solução de HF; determinar a sua composição química; e investigar a influência do Al trocável e dos óxidos de Fe na qualidade da MOS. A matéria orgânica foi concentrada com solução de HF 10 cL L-1 e posteriormente avaliada por análise elementar e espectroscopias de FTIR e de RMN 13C CP/MAS. A fração da massa recuperada (5,8 a 10 %) após tratamento com HF correlacionou-se com teor de C original do solo, enquanto a proporção de C recuperado (47 a 86 %) correlacionouse inversamente com o teor de óxidos de Fe. Esse resultado indica que parte da MOS encontra-se associada a esses minerais nesses ambientes. Os teores de estruturas C O-alquil totais (52 a 59 %) foram elevados e os valores de índice I1630/I2920(FTIR) foram baixos, evidenciando baixo grau de decomposição e de humificação da MOS desses solos.

Soils in the region of Campos de Cima da Serra, RS, have high organic matter contents (SOM) and high levels of exchangeable Al. This study aimed to investigate the SOM quality of surface samples (0-10 cm) of eight representative soils from the region (two Neossols, two Gleissols, three Cambissols, one Latosol) under native pasture. The objectives were to evaluate the sample behaviour under demineralization with HF solution, to determine the chemical composition and the influence of exchangeable Al and iron oxides on it. The SOM was concentrated with 10 % (v/v) HF solution and then submitted to elemental analysis, FTIR and 13C NMR CP/MAS spectroscopy. The recovered mass after HF treatment (5.8 to 10 %) was correlated with the soil C content, while the recovered C (47 to 86 %) was inversely correlated with the Fe oxide content. This result indicates that part of the SOM in these soils is associated to these minerals. The proportion of total C O-alkyl groups was high (52 to 59 %) and the values for the I1630/I2920 index (FTIR) were low, evidencing a low humification and decomposition degree of SOM in these soils.

Resultados de concentração de carbono (C), obtidos pelo método Walkley-Black, e resultados de concentração de nitrogênio (N) total, determinados pelo método Kjeldahl, foram comparados com os correspondentes resultados de C e N obtidos pelo método de combustão seca (analisador Elementar Vario EL), utilizando-se amostras de dez camadas de um Argissolo Vermelho até a profundidade de 107.5 cm (220-418 g argila kg-1 ao longo do perifl), manejado em sistemas de culturas de plantio direto [solo descoberto, guandu (Cajanus cajan L. Millsp.) mais milho, e lab lab (Lablab purpureum L. Sweet) mais milho]. Alta correlação (R² > 0.96) foi observada entre os resultados de C-Walkley-Black e C-combustão seca. Uma correção foi sugerida para os resultados de C-Walkley-Black (C = 1.05C W.Black + 0.47). Elevada correlação (R² > 0.96) também foi observada entre os resultados de N-Kjeldahl e N-combustão seca, não sendo necessária a aplicação de uma correção aos resultados de N-Kjeldahl. A relação entre os resultados de Walkley-Black e combustão seca e entre os resultados de Kjeldahl e combustão seca não mudaram entre amostras de solo de diferentes sistemas de manejo, diferindo dos resultados de um trabalho anterior onde a recuperação analítica de C foi influenciada por amostras oriundas de diferentes manejos, supostamente por alterações na labilidade ou recalcitrância da matéria orgânica terem afetado as reações de combustão úmida. Uma baixa correlação (R² = 0.42) foi observada entre a relação C:N baseada nas análises Walkley-Black e Kjeldahl e a relação C:N baseada na combustão seca. Os métodos de determinação de C e N não afetaram as interpretações do efeito de sistemas de manejo sobre os estoques de C e N no solo.

Organic carbon (C) concentration evaluated by the Walkley-Black method, and total nitrogen(N)concentration determined by Kjeldahl method, were compared with corresponding results of C and N concentrations obtained through the dry combustion method (Elementar Vario EL analyzer), using samples of ten soil layers down to the depth of 107.5 cm of a kaolinitic Typic Paleudult (220-418 g clay kg-1 along the profile) subjected to no-till cropping systems [fallow bare soil, pigeon pea (Cajanus cajan L. Millsp.) plus maize, and lablab (Lablab purpureum L. Sweet) plus maize]. A close correlation (R² > 0.96) was observed between the C results of the Walkley-Black and dry combustion methods, but a correction was suggested to be applied to C results of Walkley-Black (C = 1.05C W.Black + 0.47). A close correlation (R² > 0.96) was also found between results of Kjeldahl-N and dry combustion-N, but no correction was necessary to be applied. The relationships between results of Walkley-Black and dry combustion and between results of Kjeldahl and dry combustion did not change among soil samples from different management systems, in disagreement to findings of a previous study where results of analytical C recovery were influenced by samples from different managements, supposedly because changes in lability or recalcitrance of organic matter might have affected the wet combustion reactions. A poor correlation (R² = 0.42) was found between the C:N ratios based on Walkley-Black and Kjeldahl analysis and the C:N ratios based on dry combustion analysis. The methods for C and N determination did not affect the interpretation of the effects of management systems on soil C and N stocks.