Soil organic matter from the surface horizon of two Brazilian soils (a Latosol and a Chernosol), in bulk samples (in situ SOM) and in HF-treated samples (SOM), was characterized by elemental analyses, diffuse reflectance (DRIFT) and transmission Fourier transform infrared spectroscopy (T-FTIR). Humic acids (HA), fulvic acids (FA) and humin (HU) isolated from the SOM were characterized additionally by ultraviolet-visible spectroscopy (UV-VIS). After sample oxidation and alkaline treatment, the DRIFT technique proved to be more informative for the detection of […]

The structural features of humic acids (HA) after addition of organic matter from urban residues were evaluated. The HAs were extracted from the surface (0-20 cm) of an ultisol (Seropédica, RJ) and oxisol (Piraí, RJ) which had been treated with the equivalent of 80 t ha-1 (dry material) of compost from urban waste and also sewage sludge. The incubation time in the laboratory was 24 weeks under room temperature and humidity at field capacity. Tha HAs were characterized by elemental […]

The Serra do Brigadeiro State Park is covered by tropical Atlantic rain forest, as part of the Mantiqueira crystaline range. In the upper areas (above 1.600 m), a type of vegetation with singular floristic composition is found, with high endemism and a number of endangered species, here called “Campos de Altitude”. A Lithosol, a Spodosol (Podzol) and a Cambisol, all associated with “Campos de Altitude”, and a Latosol under rain forest, were sampled. These soils showed high Al saturation, low […]

Among the tools used to describe the ramified structure or the rugged and distorted surface of humic acids (HA), fractal geometry seems to be one of the most adequate to explain the conformation of humic particles (molecular aggregates). From the experimental point of view, fractal dimension (D) of natural systems may be measured through the transmitted light, not scattered or absorved (turbidimetry’τ’). The presence of fractals indicates that the system may be decomposed in parts, each part being a copy […]

This research was conducted to investigate the principal structural units from humic acids obtained from urban waste compost (AH-CRSU) and sewage sludge (AH-LETE) by pyrolysis – gas chromatography / mass spectrometry. The humic acids from sewage sludge presented most mono and diaryl esters with higher mass. The n-alcans in AH-LETE showed a shorter chain than AH-CRSU. Phthalate fragments were incorporated into the humic acid structures, probably due to an organic matter contamination by plastics. The aromatic compounds in the AH-LETE […]

Physico-chemical characteristics of humic acids obtained from urban waste (AH-CRSU) and sewage (AH-LETE) produced in the city of Rio de Janeiro, were determined through elemental analysis, total acidity, spectroscopic methods and electron scanning microscopy. The analysis of structural traits revealed some differences between the humic acids investigated. The presence of aromatic moieties was confirmed with UV-Vis spectroscopy, with more substituted systems present in the AH-LETE. IR spectroscopy showed aliphatic groups in the AH and as more complex signals due the […]

Two systems of sugar cane harvesting were compared: 1-previous burning (burned cane) and 2-straw spreading over the soil surface (green cane), over an area of Linhares Agropecuária S.A. plantation, in Linhares, Espírito Santo, Brazil. The soil was classified as Yellow Podzolic sandy over medium texture, developed from Barreiras Formation sediments. After six years of sugar cane cultivation (1989-1994), nutrient distribution, humified fractions, and soil microbial biomass dynamics were determined. The green cane system showed an increasing of soil carbon content […]

Six calcareous soil profiles (P1, P2, P3, P4, P5 and P6) were investigated with regard to their main characteristics of soil organic matter related to structural organization. The effect of degrading processes on these soils was also considered, mainly under intensive cultivation. Based on morphological in situ observation and analytical data, the profiles P1 e P2 showed organic matter with an advanced level of evolution presenting reasonable amounts of low polymerized materials (fulvic acids). Conversely, profiles P3, P4, P5 e […]