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12 páginas.-- 6 figuras.-- 4 tablas.-- 50 referencias, 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. © 2019 Sociedade Brasileira de Quimica. All Rights Reserved., This work was supported by the São Paulo Research Foundation (FAPESP, thematic project number 08/04490-4); and CNPq (project CT-Amazônia number 575795/2008-5)

Sugarcane vinasse is generated in large amounts and can be utilized to improve soil attributes, especially in areas degraded by burns. The aim of the present study was to evaluate the effects of sugarcane vinasse on physico-chemical attributes of a Cambisol managed via annual burns. Soil samples were collected from an annually burned area under pasture and used in an experiment in pots to evaluate the effects of dosages of vinasse (0, 18.8, 37.5, 56.3, 75.0, 112.5, and 150.0 m3 ha−1) on water-dispersible clay, $${\text{pH}}_{{{\text{H}}_{2} {\text{O}}}}$$ , organic matter, K+, Ca2+ + Mg2+, and K+/(Ca2+ + Mg2+). The results showed that vinasse application reduces water-dispersible clay, does not alter $${\text{pH}}_{{{\text{H}}_{2} {\text{O}}}}$$ , and increases organic matter, K+, Ca2+ + Mg2+, and K+/(Ca2+ + Mg2+). The water-dispersible clay was reduced by the formation of bonds with organic matter, which overlapped the repulsive forces intensified by the increment of K+/(Ca2+ + Mg2+). The estimated vinasse dosage that provided the minimum water-dispersible clay (69 g kg−1) was 110 m3 ha−1. Vinasse can be applied to improve the physico-chemical attributes of soils degraded by annual burns.

En este trabajo se evalúa la influencia del CaCO3 inicial en las propiedades magnéticas de sedimentos calcinado. La contribución forma parte de un estudio más amplio, acerca de la mineralogía magnética desarrollada a partir de la calcinación de sedimentos de diferentes composiciones y a distintas temperaturas. En sedimentos naturales, el incremento de la temperatura da lugar a transformaciones químico-mineralógicas que dependen, principalmente, de la composición original del material. Algunos ejemplos de esto corresponden a los suelos incendiados, a los procesos pirometamórficos y diagenéticos o a las zonas con impacto de meteoritos. Las transformaciones que ocurren durante dichos procesos se consideran similares e incluso análogas a las ocurridas en procesos industriales, como son la fabricación de ladrillos, cerámicas y cementos. Se determinaron parámetros magnéticos (susceptibilidad magnética y magnetización remanente isotermal) y elementos químicos mayoritarios en sedimentos loessoides con concentraciones contrastantes de CaCO3. El tratamiento térmico se efectuó a 1000 ºC en atmósfera de aire. Los parámetros magnéticos de las muestras antes del tratamiento térmico evidenciaron una composición magnética relativamente homogénea, dominada por la señal de minerales ferrimagnéticos (magnetita-titanomagnetita-maghemita). En contraposición, la variación de los parámetros magnéticos en las muestras calcinadas es significativa y dependiente del contenido de CaO (o bien CaCO3inicial). En las muestras que presentaron menor concentración de CaO (, In this work, the influence of the initial CaCO3, on the magnetic properties of calcined sediments, is evaluated. This contribution is part of a wider study, about magnetic mineralogy developed from sediment calcination of different compositions at diverse temperatures. High temperatures in sediments cause chemical-mineralogical transformations that depend, mainly, upon their original composition. Some examples of this are burned soils, pyrometamorphic and diagenetic processes or meteorite impact zones. Transformations could be similar, even analogous, to some industrial processes, like bricks, ceramics and cements manufacturing. The determination of magnetic parameters (magnetic susceptibility and isothermal remanent magnetization) and major chemical elements was made in sediments with contrasting amounts of CaCO3. The thermal process was performed at 1000 ºC in air atmosphere. Before heating, the behavior of magnetic composition indicates a significant homogeneity as regarding the magnetic parameters. These behaviors are undoubtedly related to the ferrimagnetic series of titanomagnetites and probably to the maghemite signal as well. In contrast, calcined samples presented magnetic records that vary noteworthy in relation to the CaO (or initial CaCO3) content. After heating, the samples with lower CaO (< 4 %) concentrations showed a magnetic signal related to antiferromagnetic minerals, like hematite. The samples with higher CaO contents (8-29 %) showed a magnetic signal related to ferrimagnetic minerals. Besides, all calcined samples showed a high contribution of nanoparticles with superparamagnetic properties., Facultad de Ciencias Naturales y Museo

Trabajo presentado en las III Jornadas de la Red Española de Compostaje, celebradas en Santiago de Compostela (España) del 26 al 29 de Junio de 2012, Se analizó la estructura o diversidad de la comunidad microbiana de suelos no adicionados y adicionados con residuos orgánicos mediante el análisis de biomarcadores moleculares (ácidos grasos de los fosfolípidos, PLFA). El estudio fue realizado con muestras de suelos procedentes de una mina, adicionadas con compost de residuos sólidos urbanos, y muestras de suelos forestales, no quemadas y quemadas, adicionadas con paja. Los resultados demostraron claramente que el análisis de los ácidos grasos de los fosfolípidos permite diferenciar, por una parte, las muestras de los suelos forestales de las de los suelos de la mina y, por otra, las muestras de los suelos de la mina no adicionados y adicionados, Xunta de Galicia (08MRU002400PR) y por el Ministerio de Ciencia e Innovación (AGL2008-02823), España.