Traçando a origem de sedimentos de reservatórios usando propriedades magnéticas no Sudeste do Brasil

Determining the origin of eroded soil is essential to design effective soil erosion control strategies which preserve the soil resource, enhance agricultural productivity, and reduce the negative impacts of soil erosion, in-field and off-field. Magnetic properties have been widely used in temperate environments to identify sediment sources, pathways and links, but there have been very few applications in tropical and subtropical environments. Therefore, in this paper we investigated reservoir sediment sources in the Upper Grande River Basin, Southeastern Brazil, using sediment tracing techniques based on magnetic parameters (low and high frequency magnetic susceptibility, frequency dependent susceptibility). The different parent materials and subtropical weathering conditions resulted in soils having different Fe oxide minerals and Fe oxide contents, promoting magnetic variability that allowed comparison and identification of possible sources of reservoir sediments in order to reduce water erosion impacts. The results indicate the suitability of magnetic properties as a tracer for soil erosion studies in tropical environments

Minerais amorfos de solos da Península Keller e Barton, Antártica Marítima

Resumo: O continente Antártico é um ambiente com características particulares e quanto a formação dos solos, o intemperismo físico predomina sobre o químicos sendo que muitos minerais formados apresentam baixa cristalinidade. Estes minerais possuem elevada área superficial específica com grande quantidade de grupos reativos de superfície e podem contribuir de forma efetiva no tamponamento de Al3+ no sistema. Quanto a caracterização, as técnicas normalmente empregadas nos estudos de mineralogia não se aplicam para estudos com minerais amorfos. Assim, o presente trabalho tem por objetivo estudar os minerais amorfos e o tamponamento de Al3+ em solos da Antártica Marítima, enfocando a sua formação em diferentes ambientes e relacionar aspectos quantitativos e qualitativos com a capacidade de adsorção de chumbo e arsênio. Foram selecionados três perfis de solo na península Keller e um na península Barton, formados sobre basaltos andesíticos e andesitos sulfatados onde foram amostrados os horizontes pedogenéticos em perfis com e sem influência ornitogênica. Na fração argila foi realizado o fracionamento dos minerais amorfos com pirofosfato de sódio (PYR) 0,05 e 0,1 mol dm-3, oxalato de amônio (OA) 0,1 e 0,2 mol dm-3 e hidróxido de sódio (NaOH) 0,25 e 0,5 mol dm-3. Após cada tratamento foi realizada a difratometria de raios X (DRX) (método do pó) e difratometria diferencial de raios X (DDRX). A cinética de liberação de Al3+ foi realizada a partir de extrações sucessivas com CuCl2 1 mol dm-3. Para determinar a CMA de Pb e As, realizou-se ensaios de adsorção na fração argila, a partir de adições sucessivas. Os parâmetros mineralógicos foram correlacionados com a CMA de Pb e As. A extração em duas etapas se mostrou eficiente na remoção dos minerais amorfos, permitindo a quantificação das fases mais lábeis e das fases mais estáveis desses minerais. A atividade ornitogênica favorece a formação de minerais amorfos em formas mais lábeis, com proporções de até 96% de óxidos extraídos com pirofosfato de sódio 0,05 mol dm-3 e de até 100% para extração com oxalato de amônio 0,1 mol dm-3. O teor de minerais amorfos na fração argila foi de até 44% nos perfis com atividade ornitogênica, demonstrando que esta atividade contribui na formação desses minerais, principalmente associados à matéria orgânica e óxidos de Fe e Al. A relação Al2O3/SiO2 ? 2 indica que em todos os perfis há predomínio de alofana. Os minerais amorfos associados à matéria orgânica são os principais responsáveis no tamponamento do Al3+ em solos com atividade ornitogênica. A CMA foi elevada para Pb (valor máximo de 411.327 mg kg-1) e baixa para As (valor máximo de 3.554 mg kg-1), sendo o perfil com influência ornitogênica de pinguins o que apresentou os maiores valores de CMA. Para o Pb2+ os principais atributos mineralógicos associados a CMA estão relacionados aos minerais amorfos ligados a matéria orgânica (MO) com destaque para os óxidos de alumínio. Para o HAsO43- além dos amorfos ligados a MO, há contribuição dos amorfos extraídos com OA e NaOH, com destaque para os óxidos de Fe. Do ponto de vista ambiental, os solos da Antártica ricos em minerais amorfos associados à atividade ornitogênica possuem maior poder filtrante para poluentes catiônicos como o Pb2+ e menor poder filtrante para poluentes aniônicos como o HAsO43-, sendo esta dinâmica fundamental para prever estratégias de preservação deste local

Tropical soils characterization at low cost and time using portable X-ray fluorescence spectrometer (pXRF): Effects of different sample preparation methods

ABSTRACT Portable X-ray fluorescence spectrometer (pXRF) has been recently adopted by the Soil Science community for uses in both field and laboratory, obtaining the total content of several chemical elements in a few seconds. Sulfuric acid digestion is an expensive and time-consuming laboratory analysis that provides contents of Fe2O3, Al2O3, SiO2, TiO2 and P2O5, important for soil studies. Due to few pXRF studies in tropical soils, this work aimed to compare contents of Fe2O3, Al2O3, SiO2, TiO2 and P2O5 obtained by pXRF with sulfuric acid digestion results, and to evaluate the effects of varying forms of preparing soil samples and scanning with pXRF on the resulting values in Brazilian soils. Soils were scanned in five conditions in-field (in situ) and in laboratory, evaluating varying sample preparation methods, particle sizes and soil moisture. Four pXRF scanning operational modes were tested. Linear regressions were adjusted between results of pXRF and sulfuric acid digestion. Equations were validated with an independent set of samples. Statistical analyses compared the methods of preparing the samples. Adequate linear models reached R2 of 0.99 and 0.89 for Fe2O3 and TiO2, respectively. Validation promoted R2 greater than 0.97 and RMSE and ME close to zero for both oxides. Statistical differences of pXRF results were found among the methods of preparing samples. pXRF spectrometer has great potential to obtain Fe2O3 and TiO2 content rapidly and economically with high correspondence with laboratory results of sulfuric acid digestion analysis. Varying methods of preparing the samples promote differences in the results of pXRF

Alkalinized sewage sludge application improves fertility of acid soils

ABSTRACT Although it is known that alkalinized sewage sludge raises the pH of acid soils, there is limited knowledge regarding its effects on other soil fertility indicators, such as P and K availability and soil organic C content. Thus, the goal of this study was to evaluate how the application of alkalinized sewage sludge affects the fertility of acid soil. Twenty sewage treatment plants were selected throughout Paraná State (Brazil), and samples of alkalinized sewage sludge and samples of the most representative agricultural soil of the region were collected (covering soils with medium, clayey or very clayey texture). Each soil was incubated for 60 days with doses of sewage sludge (0, 10, 20, 40, and 80 Mg ha-1) from its region and equivalent doses of limestone. The alkalinized sewage sludge was superior to limestone in the correction of soil acidity (pH, Al3+, and H + Al3+) and P and Ca2+ availability. The sludge also increased Mg2+ availability in all soils, K+ in seven soils and organic C in three soils. The very clayey soils (higher buffering capacity) supported higher sludge doses than did clayey and medium texture soils. The alkalinized sewage sludge application in acid soils proved to be an interesting alternative to recycling this type of waste, because it improved soil fertility and could reduce costs associated with soil management and crop fertilization

Zinc, copper and manganese availability in soils treated with alkaline sewage sludge from Paraná state (Brazil)

ABSTRACT In Paraná, most of the sludge generated in sewage treatment plants is subjected to the prolonged alkaline stabilization process. Although it is known that the alkaline sewage sludge contains micronutrients such as Zn, Cu and Mn, little is known about the availability of these elements in soils treated with this type of sewage sludge. Thus, the objective of the study was to evaluate the influence of alkaline sewage sludge from Paraná on Zn, Cu and Mn availability in soils. Twenty sewage treatment plants were selected throughout Paraná, where alkaline sewage sludge and the most representative agricultural soil of the each region were collected. Each soil was incubated for 60 days with alkaline sewage sludge rates (0, 10, 20, 40, and 80 Mg ha-1) from their region. Subsequently, Zn, Cu and Mn availability was determined using the Mehlich-1 extractant. The alkaline sewage sludge increased Zn availability and decreased Mn availability in most soils. Cu showed intermediate results, with increased availability, primarily in medium texture soils and decrease in most of the clayey soils. In soils with pH close to ideal for the plant growth, the alkaline sewage sludge rate should be carefully calculated so that there is no excessive increase in the pH and Zn, Cu and Mn imbalance