Etelvino H. Novotny

Characterization of humic acids from a Brazilian Oxisol under different tillage systems by EPR, 13C NMR, FTIR and fluorescence spectroscopy

The importance of soil organic matter functions is well known, but structural information, chemical composition and changes induced by anthropogenic factors such as tillage practices are still being researched. In the present paper were characterized Brazilian humic acids (HAs) from an Oxisol under different treatments: conventional tillage/maize-bare fallow (CT1); conventional tillage/maize rotation with soybean-bare fallow (CT2); no-till/maize-bare fallow (NT1); no-till/maize rotation with soybean-bare fallow (NT2); no-till/maize-cajanus (NT3) and no cultivated soil under natural vegetation (NC). Soil HA samples were analyzed by electron paramagnetic resonance (EPR), solid-state 13C nuclear magnetic resonance (13C NMR), Fourier transform infra-red (FTIR) and UV-Vis fluorescence spectroscopies and elemental analysis (CHNS). The FTIR spectra of the HAs were similar for all treatments. The level of semiquinone-type free radical determined from the EPR spectra was lower for treatments no-till/maize-cajanus (NT3) and noncultivated soil (1.74×1017 and 1.02×1017 spins g−1 HA, respectively), compared with 2.3×1017 spins g−1 HA for other soils under cultivation. The percentage of aromatic carbons determined by 13C NMR also decreases for noncultivated soil to 24%, being around 30% for samples of the other treatments. The solid-state 13C NMR and EPR spectroscopies showed small differences in chemical composition of the HA from soils where incorporation of vegetal residues was higher, showing that organic matter (OM) formed in this cases is less aromatic. The fluorescence intensities were in agreement with the percentage of aromatic carbons, determined by NMR (r=0.97 P<0.01) and with semiquinone content, determined by EPR (r=0.97 P<0.01). No important effect due to tillage system was observed in these areas after 5 years of cultivation. Probably, the studied Oxisol has a high clay content that offers protection to the clay–Fe–OM complex against strong structural alterations.

Pressurised pyrolysis of Miscanthus using a fixed bed reactor.

Miscanthus x giganteus was pyrolysed, in a fixed bed reactor in a constant flow of dinitrogen gas, at a rate of 13°C/min from ambient to 550°C, then held for 25 min at this temperature. The pressures employed ranged from atmospheric to 26 bar. The major compounds identified in the bio-oil were water, phenol, and phenol derivatives. The water contents impact on the usefulness of the bio-oil as a fuel. However, the phenols could provide useful platform chemicals and products. The properties of the char were determined using elemental analyses, surface area measurements using the Brunauer-Emmett-Teller equation, a calorimetric bomb, Scanning Electron Microscopy, and solid state (13)C NMR spectroscopy. The chars were highly carbonised, especially at the higher pressures, and provided thermally stable materials. Pressure impacted greatly on the surface area. Char formed at atmospheric pressure had a surface area of 162 m(2)/g, whereas that from the highest pressure applied was only 0.137 m(2)/g.

Fracionamento químico da matéria orgânica e características de ácidos húmicos de solos com horizonte a antrópico da amazônia (Terra Preta)

Amazonian dark earth soils that have anthropogenic A horizon (Au) present high natural fertility usually attributed to their high organic matter content and to their higher reactivity. In this study humic substances were quantified and the humic acids (HA) extracted from the 0-20 cm layer of Amazonian dark earth soils (Terra Preta do Indio) under forest and agricultural use were characterized. Adjacent soils with no Au horizon were also investigated. The HA were characterized through the thermogravimetric analysis, elemental composition analysis and characterization of functional groups (total, carboxylic, and phenolic). The A horizon of the anthropogenic soils presented higher total carbon level compared to adjacent soils. Among the humic fractions, the humin was the most abundant. The humic acid fraction (HA) was the dominant among the alkaline soluble fractions. The humic acids of the anthropogenic soils, both under forest and cultivation, showed higher humification degree compared to the non-anthropogenic soils. The agricultural cultivation affected the humic acids stability and reactivity in the anthropogenic soils.

Characterisation of the products from pyrolysis of residues after acid hydrolysis of Miscanthus

Platform chemicals such as furfural and hydroxymethylfurfural are major products formed during the acid hydrolysis of lignocellulosic biomass in second generation biorefining processes. Solid hydrolysis residues (HR) can amount to 50 wt.% of the starting biomass materials. Pyrolysis of the HRs gives rise to biochar, bio-liquids, and gases. Time and temperature were variables during the pyrolysis of HRs in a fixed bed tubular reactor, and both parameters have major influences on the amounts and properties of the products. Biochar, with potential for carbon sequestration and soil conditioning, composed about half of the HR pyrolysis product. The amounts (11-20 wt.%) and compositions (up to 77% of phenols in organic fraction) of the bio-liquids formed suggest that these have little value as fuels, but could be sources of phenols, and the gas can have application as a fuel.

Soil management system effects on size fractionated humic substances

Abstract The humic substances (HS) of two Brazilian Oxisols, one under native grassland (NG) and the other submitted to a long-term (19-year) tillage systems experiment including no-tillage (NT), minimal tillage (MT) and an adjacent eucalyptus-planted forest (F), were extracted with sodium pyrophosphate, analysed and fractionated by exclusion chromatography on controlled pore glass (CPG). Chromatographic analysis of HS was performed at 400 nm (visible region), the resulting chromatograms deconvoluted and statistical analysis of data made using multivariate methods (factor and Pearson correlation analysis). Increase of tillage intensity, estimated by factor analysis, resulted in a general HS content decrease, not affecting soil C content. Tillage increased the relative proportion of small molecular size HS, determined directly by CPG and indirectly by the relative increase of fulvic acids (FA) content (increase of fulvic acids/humic acids ratio). This suggests that tillage caused preferential degradation of large molecular size HS and/or a neo-synthesis of small HS due to increased fresh-carbon input partially induced by liming and fertilisation. The HS fractionation method on CPG permitted gray humic acids (GHA) separation into two distinct fractions. The larger molecular size fraction showed an unusual high E 4 /E 6 ratio, possibly due to a small conjugation of aromatic rings.

Effects of humidity and metal ions on the free radicals analysis of peat humus

The effects of humidity and metal ions in the determination of humic organic free radicals concentration (HOFRC) were studied by electron paramagnetic resonance (EPR). Increasing the sample humidity caused a decrease in both HOFRC, probably due to free radicals recombination, and in the derivative peak-to-peak line width (ΔH), probably due to a higher spin–spin relaxation time (T2) as the molecular mobility increased (shorter correlation time). Diamagnetic ions (Na+, Zn2+ and Al3+) did not affect the HOFRC, while paramagnetic ions (Fe3+, Mn2+ and Cu2+) induced an intense HOFRC decrease. This effect was associated with dipolar-relaxation enhancement at high (above 0.01%) paramagnetic ion concentrations, since the inhomogeneity parameter decreased to less than 1. Further, a possible exchange interaction and/or shift in the free radicals equilibrium reactions might have occurred at low paramagnetic ion concentrations (below 0.01%).

Molecular Characteristics of Humic Acids Isolated from Vermicomposts and Their Relationship to Bioactivity

Vermitechnology is an effective composting method, which transforms biomass into nutrient-rich organic fertilizer. Mature vermicompost is a renewable organic product containing humic substances with high biological activity. The aim of this study was to assess the chemical characteristics and the bioactivity of humic acids isolated from different vermicomposts produced with either cattle manure, sugar cane bagasse, sunflower cake from seed oil extraction, or filter cake from a sugar cane factory. More than 200 different molecules were found, and it was possible to identify chemical markers on humic acids according to the nature of the organic source. The large hydrophobic character of humic extracts and the preservation of altered lignin derivatives confer to humic acids the ability to induce lateral root emergence in maize seedlings. Humic acid-like substances extracted from plant biomass residues represent an additional valuable product of vermicomposting that can be used as a plant growth promoter.

Tracking thermal degradation on passion fruit juice through Nuclear Magnetic Resonance and chemometrics.

Thermal food processing mainly aims to control microorganism in order to extend its shelf life. However, it may induce chemical and nutritional changes in foodstuff. The Nuclear Magnetic Resonance (NMR) coupled to multivariate analysis was used to evaluate the effect of different thermal processing conditions (85 and 140°C for 4; 15; 30; and 60s) on the passion fruit juice using an Armfield pasteurizer. Through this approach it was possible to identify the changes in the juice composition. The temperature and the time lead to a hydrolysis of the sucrose to glucose and fructose. Additionally, juice submitted to 140°C for 60s results in the degradation of the sucrose and the formation of 5-(hydroxymethyl)-2-furfural (HMF). Despite no novel chemical marker has been identified, the 1H NMR chemometrics approach may contribute in the choice of the temperature and time to be employed in the juice processing.

Molecular and morphological characterization of hydrochar produced by microwave-assisted hydrothermal carbonization of cellulose

The objective of this work was to characterize the morphology and molecular composition of the hydrochar produced by microwave-assisted hydrothermal carbonization of cellulose. The produced hydrochar consists mainly of aggregate microspheres with about 2.0 µm in diameter, with aliphatic and aromatic structures and the presence of carbonyl functional groups. The aromatic groups are formed mainly by benzofuran-like structures, being chemically different from common cellulose char. Microwave-assisted hydrothermal carbonization yields a functionalized carbon-rich material similar to that produced by the conventional hydrothermal process.

CPMAS 13C NMR Characterization of Leaves and Litters from the Reafforestated Area of Mustigarufi in Sicily (Italy)

Reafforestation is generally based on the planting of exotic fast growing tree species suitable for adapting to even harsh environments. Once the introduced plants ameliorate soil conditions, they can be progressively replaced by au- tochthonous plant species. Reafforestation is applied worldwide. However, only few studies on the effect of reafforesta- tion on lands from Mediterranean regions are available. This paper reports the characterization by cross polarization 13 C NMR spectroscopy of fresh leaves and superficial litters from a reafforestated area in central Sicily (Italy). NMR assign- ment is attempted. A differentiation among the molecular systems within leaves and litters is also done on the basis of NMR assessment. Results showed that the main differences among the leaves of four forest trees (two eucalyptus spp., one cypress sp. and one pine sp.) occur in the distribution of the aromatic and alkyl carbons. In particular, the alkyl moie- ties in the eucalyptus spp. leaves were attributed to branched structures belonging to the eucalyptus oil, whereas linear fatty acids were more representetive in the NMR spectra of pine and cypress leaves. In addition, the aromatic carbons of the conifer leaves were assigned not only to lignin- and tannin-like structures, but also to common olefin carbons in un- saturated fatty acids and abietic acid-like systems. The spectra of the litters resembled, as expected, those of the leaves. However, the presence of very large carbohydrate NMR signals suggested that degradation processes were still ongoing in litters. A comparative evaluation of CPMAS 13 C NMR spectra was done by applying principal component analysis. This paper confirmed the suitability of CPMAS 13 C NMR spectroscopy in evaluating the differences among natural bio-masses